How to Easily Set Up a Full-Featured Mail Server on CentOS 8 with iRedMail

Setting up your own email server on Linux from scratch is a pain in the butt if you are not an advanced user. This tutorial will be showing you how to use iRedMail to quickly set up a full-featured mail server on CentOS 8, saving you lots of time and headaches.

What is iRedMail?

iRedMail is a shell script that automatically installs and configures all necessary mail server components on your Linux/BSD server, thus eliminating manual installation and configuration. With iRedMail, you can easily create unlimited mailboxes and unlimited mail domains in a web-based admin panel. Mailboxes can be stored in MariaDB/MySQL, PostgreSQL database, or OpenLDAP. The following is a list of open-source software that will be automatically installed and configured by iRedMail.

  • Postfix SMTP server
  • Dovecot IMAP server
  • Nginx web server to serve the admin panel and webmail
  • OpenLDAP, MySQL/MariaDB, or PostgreSQL for storing user information
  • Amavised-new for DKIM signing and verification
  • SpamAssassin for anti-spam
  • ClamAV for anti-virus
  • Roundcube webmail
  • Fail2ban for protecting SSH
  • mlmmj mailing list manager
  • Netdata server monitoring
  • iRedAPD Postfix policy server for greylisting

Step 1: Choose the Right Hosting Provider and Buy a Domain Name

To set up a full-featured email server with iRedMail, you need a server with at least 3GB RAM, because after the installation, your server will use more than 2GB of RAM.

It is highly recommended that you install iRedMail on a clean install of CentOS 8 server.

This tutorial is done on a $9/month Kamatera VPS (virtual private server) with 1 CPU and 3GB RAM. They offer a 30-day free trial.

Kamatera is a very good option to run a mail server because

  • They don’t block port 25, so you can send unlimited emails (transactional email and newsletters) without spending money on SMTP relay service. Kamatera doesn’t have any SMTP limits. You can send a million emails per day.
  • The IP address isn’t on any email blacklist. (At least this is true in my case. I chose the Dallas data center.) You definitely don’t want to be listed on the dreaded Microsoft Outlook IP blacklist or the spamrats blacklist. Some blacklists block an entire IP range and you have no way to delist your IP address from this kind of blacklist.
  • You can edit PTR record to improve email deliverability.
  • They allow you to send newsletters to your email subscribers with no hourly limits or daily limits, whatsoever.
  • You can order multiple IP addresses for a single server. This is very useful for folks who need to send a large volume of emails. You can spread email traffic on multiple IP addresses to achieve better email deliverability.

Other VPS providers like DigitalOcean blocks port 25. DigitalOcean would not unblock port 25, so you will need to set up SMTP relay to bypass blocking, which can cost you additional money. If you use Vultr VPS, then port 25 is blocked by default. They can unblock it if you open a support ticket, but they may block it again at any time if they decide your email sending activity is not allowed. Vultr actually may re-block it if you use their servers to send newsletters.

Go to Kamatera website to create an account, then create your server in your account dashboard.

kamatera server types

I recommend following the tutorial linked below to properly set up your Linux VPS server on Kamatera.

Once you created a server, Kamatera will send you an email with the server SSH login details. To log into your server, you use an SSH client. If you are using Linux or macOS on your computer, then simply open up a terminal window and run the following command to log into your server. Replace with your server’s IP address.

ssh [email protected]

You will be asked to enter the password.

You also need a domain name. I registered my domain name from NameCheap because the price is low and they give whois privacy protection free for life.

Step 2: Creating DNS MX Record

The MX record specifies which host or hosts handle emails for a particular domain name. For example, the host that handles emails for is If someone with a Gmail account sends an email to [email protected], then Gmail server will query the MX record of When it finds out that is responsible for accepting email, it then query the A record of to get the IP address, thus the email can be delivered.

In your DNS manager, create a MX record for your domain name. Enter @ in the Name field to represent the main domain name, then enter in the Value field.

iredmail email server create MX record

Note: The hostname for MX record can not be an alias to another name. Also, It’s highly recommended that you use hostnames, rather than bare IP addresses for MX record.

Your DNS manager may require you to enter a preference value (aka priority value). It can be any number between 0 and 65,356. A small number has higher priority than a big number. It’s recommended that you set the value to 0, so this mail server will have the highest priority for receiving emails. After creating MX record, you also need to create an A record for , so that it can be resolved to an IP address. If your server uses IPv6 address, be sure to add AAAA record.

Hint: If you use Cloudflare DNS service, you should not enable the CDN feature when creating A record for Cloudflare does not support SMTP proxy.

Step 3: Configuring Hostname

Log into your server via SSH, then run the following command to update existing software packages.

sudo dnf update -y

I strongly recommend creating a sudo user for managing your server rather than using the default root user. Run the following command to create a user. Replace username with your preferred username.

sudo adduser username

Set a password for this user.

sudo passwd username

Add this user to the wheel group in order to use sudo.

sudo gpasswd -a username wheel

Switch to the new user.

su - username

Next, set a fully qualified domain name (FQDN) for your server with the following command.

sudo hostnamectl set-hostname

We also need to update /etc/hosts file with a command-line text editor like Nano.

sudo nano /etc/hosts

Edit it like below. (Use arrow keys to move the cursor in the file.) localhost

Save and close the file. (To save a file in Nano text editor, press Ctrl+O, then press Enter to confirm. To close the file, press Ctrl+X.)

To see the changes, re-login and run the following command to see your hostname.

hostname -f

Step 4: Setting up Mail Server on CentOS 8 with iRedMail

Run the following commands to download the latest version of iRedMail script installer from its Github repository.

sudo dnf install wget tar -y


Extract the archived file.

tar xvf 1.5.0.tar.gz

Then cd into the newly-created directory.

cd iRedMail-1.5.0/

Add executable permission to the script.

chmod +x

Next, run the Bash script with sudo privilege.

sudo bash

The mail server setup wizard will appear. Use the Tab key to select Yes and press Enter.


The next screen will ask you to select the mail storage path. You can use the default one /var/vmail, so simply press Enter.


Then choose whether you want to run a web server. It’s highly recommended that you choose to run a web server because you need the web-based admin panel to add email accounts. Also it allows you to access the Roundcube webmail. By default, Nginx web server is selected, so you can simply press Enter. (An asterisk indicates the item is selected.)


Then select the storage backend for email accounts. Choose one that you are familiar with. This tutorial chose MariaDB. Press up and down arrow key and press the space bar to select.

centos 8 email server

If you selected MariaDB or MySQL, you will need to set the MySQL root password.

centos 8 mail server

Next, enter your first mail domain. You can add additional mail domains later in the web-based admin panel. This tutorial assumes that you want an email account like [email protected]. In that case, you need to enter here, without sub-domain. Do not press the space bar after your domain name. I think iRedMail will copy the space character along with your domain name, which can result in installation failure.

set up mail server on centos 8

Next, set a password for the mail domain administrator.


Choose optional components. By default, all of the 4 items are selected. So simply press Enter.

centos 8 iredmail optional components

Now you can review your configurations. Type Y to begin the installation of all mail server components.

centos 8 iredmail review config

Make sure you see no error in the installation process. If there are errors, it’s better to reinstall the OS and then reinstall iRedMail on your server, or your mail server might not work properly.

At the end of the installation, choose y to use firewall rules provided by iRedMail and restart the firewall.

centos 8 iredmail firewall rules mysql config

Now iRedMail installation is complete. You will be notified the URL of webmail, web admin panel and the login credentials. The file contains important information about your iRedMail server.

iredmail url of installed web applications

Reboot your CentOS 8 server.

sudo shutdown -r now

Once your server is back online, you can visit the web admin panel.

Note that in the above URL, the sub-directory for accessing the admin panel is /iredadmin/, not /iredmail/. And because it’s using a self-signed TLS certificate, you need to add security exception in your web browser.

Step 5: Installing Let’s Encrypt TLS Certificate

Since the mail server is using a self-signed TLS certificate, both desktop mail client users and webmail client users will see a warning. To fix this, we can obtain and install a free Let’s Encrypt TLS certificate.

Obtaining the Certificate

First, log into your server again via SSH and run the following commands to install Let’s Encrypt (certbot) client on CentOS 8.

sudo dnf install certbot python3-certbot-nginx -y

iRedMail has already configured TLS settings in the default Nginx virtual host, so here I recommend using the webroot plugin, instead of nginx plugin, to obtain the certificate. Run the following command. Replace with the red text with your own email address and hostname.

sudo certbot certonly --webroot --agree-tos --email [email protected] -d -w /var/www/html/

When it asks you if you want to receive communications from EFF, you can choose No.


If everything went well, you will see the following text indicating that you have successfully obtained a TLS certificate. Your certificate and chain have been saved at /etc/letsencrypt/live/ directory.

iredmail tls certificate

Failure to Obtain TLS Certificate

If certbot failed to obtain TLS certificate, maybe it’s because your DNS records are not propagated to the Internet. Depending on the domain registrar you use, your DNS record might be propagated instantly, or it might take up to 24 hours to propagate. You can go to, enter your mail server’s hostname ( to check DNS propagation.

Installing the Certificate in Nginx

After obtaining a TLS certificate, let’s configure Nginx web server to use it. Edit the SSL template file.

sudo nano /etc/nginx/templates/ssl.tmpl

Find the following 2 lines.

ssl_certificate /etc/pki/tls/certs/iRedMail.crt;
ssl_certificate_key /etc/pki/tls/private/iRedMail.key;

Replace them with:

ssl_certificate /etc/letsencrypt/live/;
ssl_certificate_key /etc/letsencrypt/live/;

Save and close the file. Then test nginx configuration and reload.

sudo nginx -t

sudo systemctl reload nginx

Visit iRedMail admin panel again, your web browser won’t warn you any more because Nginx is now using a valid TLS certificate.


Installing TLS Certificate in Postfix and Dovecot

We also need to configure Postfix SMTP server and Dovecot IMAP server to use the Let’s Encrypt issued certificate so that desktop mail client won’t display security warning. Edit the main configuration file of Postfix.

sudo nano /etc/postfix/

Find the following 3 lines. (line 95, 96, 97).

smtpd_tls_key_file = /etc/pki/tls/private/iRedMail.key
smtpd_tls_cert_file = /etc/pki/tls/certs/iRedMail.crt
smtpd_tls_CAfile = /etc/pki/tls/certs/iRedMail.crt

Replace them with:

smtpd_tls_key_file = /etc/letsencrypt/live/
smtpd_tls_cert_file = /etc/letsencrypt/live/
smtpd_tls_CAfile = /etc/letsencrypt/live/

Save and close the file. Then reload Postfix.

sudo systemctl reload postfix

Next, edit the main configuration file of Dovecot.

sudo nano /etc/dovecot/dovecot.conf

Fine the following 2 lines. (line 47, 48)

ssl_cert = </etc/pki/tls/certs/iRedMail.crt
ssl_key = </etc/pki/tls/private/iRedMail.key

Replace them with:

ssl_cert = </etc/letsencrypt/live/
ssl_key = </etc/letsencrypt/live/

Save and close the file. Then reload dovecot.

sudo systemctl reload dovecot

From now on, desktop mail users won’t see security warnings.

Step 6: Sending Test Email

Log into iredadmin panel with the postmaster mail account ([email protected]). In the Add tab, you can add additional domains or email addresses.

add email addresses in iredadmin

If you see “no domain under control” error, please refer to this article.

After you create a user, you can visit the Roundcube webmail address and login with the new mail user account.

iredmail roundcube webmail

Now you can test email sending and receiving. Please note that you may need to wait a few minutes to receive emails because iRedMail by default enables greylisting, which is a way to tell other sending SMTP servers to try again in a few minutes. The following line in the mail log file /var/log/maillog indicates greylisting is enabled.

Recipient address rejected: Intentional policy rejection, please try again later;

Checking if ClamAV is Running

ClamAV is used to scan viruses in email messages. ClamAV can use a fair amount of RAM. If there’s not enough RAM on your server, ClamAV won’t work properly, which will prevent your mail server from sending emails. You can check its status with:

systemctl status clamd@amavisd

If your ClamAV is always activating like below, you have a problem.

systemctl status clamd@amavisd

Check ClamAV logs.

sudo journalctl -eu clamd@amavisd

If you see the following line in the logs, that means your server doesn’t have enough RAM to run ClamAV.

daemonize() failed: Cannot allocate memory

You can add a swap file to your server to increase the total RAM on your server. (Note that using swap space on the server will degrade server performance. If you want better performance, you should upgrade the physical RAM instead of using swap space.)

To add swap space on the server, first, use the fallocate command to create a file. For example, create a file named swapfile with 1G capacity in root file system:

sudo fallocate -l 1G /swapfile

Then make sure only root can read and write to it.

sudo chmod 600 /swapfile

Format it to swap:

sudo mkswap /swapfile


Setting up swapspace version 1, size = 1024 MiB (1073737728 bytes)
no label, UUID=0aab5886-4dfb-40d4-920d-fb1115c67433

Enable the swap file

sudo swapon /swapfile

Wait a few seconds, your ClamAV should be active (running), and it won’t prevent your mail server from sending emails.

systemctl status clamd@amavisd

clamav memory usage

To mount the swap space at system boot time, edit the /etc/fstab file.

sudo nano /etc/fstab

Add the following line at the bottom of this file.

/swapfile    swap    swap     defaults    0   0

Save and close the file. Then reload systemd.

sudo systemctl daemon-reload

Step 7: Checking If Port 25 (outbound) is blocked

Your ISP or hosting provider won’t block incoming connection to port 25 of your server, which means you can receive emails from other mail servers. However, many ISP/hosting providers block outgoing connection to port 25 of other mail servers, which means you can’t send emails.

If your email didn’t arrive at your other email address such as Gmail, then you can use the telnet utility to check if port 25 (outbound) is blocked. Install telnet on CentOS 8 with:

sudo dnf install telnet

Then run the following command on your mail server.

telnet 25

If port 25 (outbound) is not blocked, you would see messages like below, which indicates a connection is successfully established. (Hint: Type in quit and press Enter to close the connection.)

Connected to
Escape character is '^]'.
220 ESMTP y22si1641751pll.208 - gsmtp

If port 25 (outbound) is blocked, you would see something like:

Trying 2607:f8b0:400e:c06::1a...
telnet: Unable to connect to remote host: Connection timed out

In this case, your Postfix can’t send emails to other SMTP servers. Ask your ISP/hosting provider to open it for you. If they refuse your request, you need to set up SMTP relay to bypass port 25 blocking.

Still Can’t Send Email?

If port 25 (outbound) is not blocked, but you still can’t send emails from your own mail server to your other email address like Gmail, then you should check the mail log (/var/log/mail.log).

sudo nano /var/log/mail.log

For example, some folks might see the following lines in the file.

host[2404:6800:4003:c03::1b] said: 550-5.7.1 [2a0d:7c40:3000:b8b::2] Our system has detected that 550-5.7.1 this message does not meet IPv6 sending guidelines regarding PTR 550-5.7.1 records and authentication. Please review 550-5.7.1 for more information

This means your mail server is using IPv6 to send the email, but you didn’t set up IPv6 records. You should go to your DNS manager, set AAAA record for, then you should set PTR record for your IPv6 address, which is discussed in step 9.

How to Disable Greylisting

By default, iRedMail has enabled greylisting, which tells other sending SMTP servers to try again in a few minutes. This is mainly useful to block spam, but it also degrades user experience. If you prefer to disable greylisting, follow the instructions below.

Add write permission to the /opt/iredapd/ file.

sudo chmod 600 /opt/iredapd/

Then edit the configuration file.

sudo nano /opt/iredapd/

Find the following line.

plugins = ["reject_null_sender", "wblist_rdns", "reject_sender_login_mismatch", "greylisting", "throttle", "amavisd_wblist", "sql_alias_access_policy"]

Remove "greylisting" from the list. Save and close the file. Then restart iredapd.

sudo systemctl restart iredapd

Change the configuration file back to read-only mode.

sudo chmod 400 /opt/iredapd/

Step 8: Using Mail Clients on Your Computer or Mobile Device

Fire up your desktop email client such as Mozilla Thunderbird and add a mail account. If Thunderbird found your mail server configuration like below, simply click Done button and you will be able to read and send emails.

mozilla thunderbird set up an existing email account

If Thunderbird didn’t found your mail server configuration, then click Manual config button to enter your mail server details.

  • In the incoming server section, select IMAP protocol, enter as the server name, choose port 143 and STARTTLS. Choose normal password as the authentication method.
  • In the outgoing section, select SMTP protocol, enter as the server name, choose port 587 and STARTTLS. Choose normal password as the authentication method.

ubuntu postfix dovecot letsencrypt https

Hint: You can also use IMAP on port 993 with SSL/TLS encryption.

Fail2ban Blocking Your Own IP Address

If you made a mistake and failed to log in to mail server multiple times, then the Fail2ban service on the mail server might block your IP address. You can add your IP address to whitelist by editing the jail.local file.

sudo nano /etc/fail2ban/jail.local

Add your own IP address to the ignore list like below. Replace with your real IP address.

ignoreip =

Save and close the file. Then restart Fail2ban.

sudo systemctl restart fail2ban

Step 9: Improving Email Deliverablity

To prevent your emails from being flagged as spam, you should set PTR, SPF, DKIM and DMARC records.

PTR record

A pointer record, or PTR record, maps an IP address to a FQDN (fully qualified domain name). It’s the counterpart to the A record and is used for reverse DNS lookup, which can help with blocking spammers. Many SMTP servers reject emails if no PTR record is found for the sending server.

To check the PTR record for an IP address, run this command:

dig -x IP-address +short


host IP-address

PTR record isn’t managed by your domain registrar. It’s managed by the organization that gives you an IP address. Because you get IP address from your hosting provider or ISP, not from your domain registrar, so you must set PTR record for your IP in the control panel of your hosting provider, or ask your ISP. Its value should be your mail server’s hostname: If your server uses IPv6 address, be sure to add a PTR record for your IPv6 address as well.

To edit the reverse DNS record for your Kamatera VPS, log into the Kamatera client area, then open a support ticket and tell them to add PTR record for your server IP addresss to point the IP address to It’s not convenient, you might think, but this is to keep spammers away from the platform, so legitimate email senders like us will have a great IP reputation.

SPF Record

SPF (Sender Policy Framework) record specifies which hosts or IP addresses are allowed to send emails on behalf of a domain. You should allow only your own email server or your ISP’s server to send emails for your domain. In your DNS management interface, create a new TXT record like below.

mail server spf record


  • TXT indicates this is a TXT record.
  • Enter @ in the name field to represent the main domain name.
  • v=spf1 indicates this is a SPF record and the version is SPF1.
  • mx means all hosts listed in the MX records are allowed to send emails for your domain and all other hosts are disallowed.
  • ~all indicates that emails from your domain should only come from hosts specified in the SPF record. Emails that are from other hosts will be flagged as forged.

To check if your SPF record is propagated to the public Internet, you can use the dig utility on your Linux machine like below:

dig txt

The txt option tells dig that we only want to query TXT records.

DKIM Record

DKIM (DomainKeys Identified Mail) uses a private key to digitally sign emails sent from your domain. Receiving SMTP servers verify the signature by using the public key, which is published in the DNS DKIM record.

The iRedMail script automatically configured DKIM for your server. The only thing left to do is creating DKIM record in DNS manager. Run the following command to show the DKIM public key.

sudo amavisd -c /etc/amavisd/amavisd.conf showkeys

The DKIM public key is in the parentheses.


Then in your DNS manager, create a TXT record, enter dkim._domainkey in the name field. Copy everything in the parentheses and paste into the value field. Delete all double quotes and line breaks.

amavisd-new ubuntu

After saving your changes, run the following command to test if your DKIM record is correct.

sudo amavisd -c /etc/amavisd/amavisd.conf testkeys

If the DKIM record is correct, the test will pass.

TESTING#1 => pass

Note that your DKIM record may need sometime to propagate to the Internet. Depending on the domain registrar you use, your DNS record might be propagated instantly, or it might take up to 24 hours to propagate. You can go to, enter dkim as the selector and enter your domain name to check DKIM record propagation.

DMARC Record

DMARC stands for Domain-based Message Authentication, Reporting and Conformance. DMARC can help receiving email servers to identify legitimate emails and prevent your domain name from being used by email spoofing.

To create a DMARC record, go to your DNS manager and add a TXT record. In the name field, enter _dmarc. In the value field, enter the following. (You should create the [email protected] email address.)

v=DMARC1; p=none; pct=100; rua=mailto:[email protected]

create dmarc record txt

The above DMARC record is a safe starting point. If you want to read the full explanation of DMARC, please check the following article. Note that this is optional.

Step 10: Testing Email Score and Placement

After creating PTR, SPF, DKIM record, go to You will see a unique email address. Send an email from your domain to this address and then check your score. As you can see, I got a perfect score. In the test result, you should check if your PTR record, SPF and DKIM record is valid.

Testing Email Score and can only show you a sender score. There’s a another service called GlockApps that allow you to check if your email is landed in the recipient’s inbox or spam folder, or rejected outright. It supports many popular email providers like Gmail, Outlook, Hotmail, YahooMail, iCloud mail, etc.


Email is Rejected by Microsoft Mailbox?

Microsoft uses an internal blacklist that blocks many legitimate IP addresses. If your emails are rejected by Outlook or Hotmail, you need to follow the tutorial linked below to bypass Microsoft Outlook blacklist.

What if Your Emails Are Still Being Marked as Spam?

I have more tips for you in this article: How to stop your emails being marked as spam. Although it will take some time and effort, your emails will eventually be placed in inbox after applying these tips.

Adding Multiple Mail Domains

I wrote this article to show you how to add multiple mail domains in iRedMail.

Enabling SMTPS Port 465

If you are going to use Microsoft Outlook client, then you need to enable SMTPS port 465 in Postfix SMTP server.


First, please use a VPS with at least 4GB RAM. Running iRedMail on a 1GB RAM VPS will cause the database, SpamAssassin, or ClamAV to be killed because of out-of-memory problem. If you really want to use a 1GB RAM VPS, you are going to lose incoming emails and have other undesirable outcomes.

If the iRedMail web interface isn’t accessible, like a 502 gateway error, you should check the Nginx logs in /var/log/nginx/ directory to find clues. You may also want to check the mail log /var/log/maillog.

Check if the various services are running.

systemctl status postfix

systemctl status dovecot

systemctl status nginx

systemctl status mariadb

systemctl status clamd@amavisd

systemctl status amavisd

If you enabled the firewall, you should open the following ports in the firewall.

HTTP port:  80
HTTPS port: 443
SMTP port:  25
Submission port: 587 (and 465 if you are going to use Microsoft Outlook mail client)
IMAP port:  143 and 993

If you would like to use the UFW firewall, check my guide here: Getting started with UFW firewall on Debian and Ubuntu.

How to Renew TLS Certificate

Let’s Encrypt issued TLS certificate is valid for 90 days only and it’s important that you set up a Cron job to automatically renew the certificate. You can run the following command to renew certificate.

sudo certbot renew -w /var/www/html

You can use the --dry-run option to test the renewal process, instead of doing a real renewal.

sudo certbot renew -w /var/www/html --dry-run

If you see the following error when renewing TLS certificate.

The client lacks sufficient authorization :: Invalid response

Then you need to create the hidden directory.

sudo mkdir -p /var/www/html/.well-known/acme-challenge

And set www-data as the owner of the webroot.

sudo chown www-data:www-data /var/www/html/ -R

Also, edit the SSL virtual host /etc/nginx/sites-enabled/00-default-ssl.conf. Add the following lines.

location ~ /.well-known/acme-challenge {
     root /var/www/html/;
     allow all;

iredmail letsencrypt renew

Save and close the file. Test Nginx configuration and reload.

sudo nginx -t
sudo systemctl reload nginx

Create Cron Job

If now the dry run is successful, you can create Cron job to automatically renew certificate. Simply open root user’s crontab file.

sudo crontab -e

Then add the following line at the bottom of the file.

@daily certbot renew -w /var/www/html --quiet && systemctl reload postfix dovecot nginx

Reloading Postfix, Dovecot and Nginx is necessary to make these programs pick up the new certificate and private key.

For Advanced Users

You may want to customize the SpamAssassin content filter to better detect spam.

If your website and mail server are running on two different VPS (virtual private server), you can set up SMTP relay between your website and mail server, so that your website can send emails through your mail server. See the following article.

Wrapping Up

That’s it! I hope this tutorial helped you set up a mail server on CentOS 8 with iRedMail. As always, if you found this post useful, then subscribe to our free newsletter to get more tips and tricks. Take care 🙂

Rate this tutorial
[Total: 3 Average: 5]

23 Responses to “How to Easily Set Up a Full-Featured Mail Server on CentOS 8 with iRedMail

  • Kurnia Ramadhan
    4 years ago

    do you have tutorial how to implementation Sendinblue as a smtp relay with iRedMail? thx

  • Hi Xiao, thank you for the great tutorial!

    A quick questions: has iredmail already implemented the “7 Effective Tips for Blocking Email Spam with Postfix”?

    Thanks a lot!

    • Xiao Guoan (Admin)
      4 years ago

      iRedMail has almost the same spam filters as described in the “7 Effective Tips for Blocking Email Spam with Postfix” article. However, iRedMail doesn’t have a DMARC checker. I will update my DMARC tutorial.

      • Thanks a lot for your reply, Xiao! Look forward to your DMARC tutorial update.

        Another thought here, SOGo seems to be quite useful for calendar and contact sync and sharing. It would be nice to add this part in this tutorial. Thank you again.

    • Xiao Guoan (Admin)
      4 years ago

      Hello DJ,

      I just updated my CentOS OpenDMARC tutorial: Set Up OpenDMARC with Postfix on CentOS/RHEL to Block Email Spoofing

  • Thanks for making this tutorial! Everything delivered was on point. One suggestion 🙂 It would be great if you can post some content for backing up and restoring the email server.

  • Raphael3922
    4 years ago


    Thank you for your wonderful tutorial, which is very clear, on installing Iredmail on Centos7 / 8.

    I work :
    1 °) on a Ste SoYouStart server which manages the site of my domain name:
    SoYouStart server
    Centos: 7.8.2003
    Webmin: 1.955
    Virtualmin: 6.12
    Hostname: (WWW.XXX.YYY.ZZZ)
    This server manages in fact (with Bind from Webmin / Virtualmin) the Dns of this domain name.

    2 °) on a Ste Kimsufi server which manages the mail service (by Iredmail)
    With like Ip4: AAA.BBB.CCC.DDD
    With like Ip6: azerty
    Hostname: (AAA.BBB.CCC.DDD)

    I installed the following PTRs on the Kimsufi server configuration:
    DKIM key provided by the order:

    amavisd -c /etc/amavisd/amavisd.conf showkeys

    We have

    (“v = DKIM1; k = rsa; t = s; p = aqwxszEDCVFRtgbNHY”
    “muDrFSOFIhP / ZJgNeFF5qqTpz3XT9VrVC9wocyS82j20MaCPqcfNRwDRdfko2AZk0YN4QCh + 6kXlvQ1W”
    “UqSDguuzXg / IdY + 5mRtUvWmXwXcDrwYBRDjOEYOQ / xz0mbpyVndT / wTtvLatNGm3uSOFUM3gcY12cHSA”
    “7nEmF07WcELQurHk / HHUr0gi4LcH82p8fqeuRI3mUibRvjz6aaHytOtjzaihSMQnrut24wGxc3zmZe4A”
    “iyLOX0FXhWDIltYDzVAyWu7USzZ / dRWZmwZtUkEXKT1KXASA3q / buetZHFXV4WH8 + / qRz0hXo6Ax5LD /”

    In the Dns records due to the virtual server of the domain on the Ste SoYouStart server, I try to set up the following SPF and DKIM records: 36000 IN TXT “v = spf1 a mx a: ip4: WWW.XXX.YYY.ZZZ ip4: AAA.BBB.CCC.DDD ip6: azerty ip6: qsdfgh -all” IN TXT (“v = DKIM1; k = rsa; t = s; p = aqwxszEDCVFRtgbNHY”
    “muDrFSOFIhP / ZJgNeFF5qqTpz3XT9VrVC9wocyS82j20MaCPqcfNRwDRdfko2AZk0YN4QCh + 6kXlvQ1W”
    “UqSDguuzXg / IdY + 5mRtUvWmXwXcDrwYBRDjOEYOQ / xz0mbpyVndT / wTtvLatNGm3uSOFUM3gcY12cHSA”
    “7nEmF07WcELQurHk / HHUr0gi4LcH82p8fqeuRI3mUibRvjz6aaHytOtjzaihSMQnrut24wGxc3zmZe4A”
    “iyLOX0FXhWDIltYDzVAyWu7USzZ / dRWZmwZtUkEXKT1KXASA3q / buetZHFXV4WH8 + / qRz0hXo6Ax5LD /”

    It doesn’t seem to be working. Does anyone have an idea, a remark, an idea of ​​modification? Please thank you



    • Xiao Guoan (Admin)
      4 years ago

      If you use BIND authoritative DNS server, see the following screenshot for an example DKIM record.


      • Raphael3922
        4 years ago


        Dkim registration verifies, modifies and validates.
        My Iredmail installation is working thank you very much for your help and your responsiveness.


  • Raphael
    4 years ago


    Thank you for this excellent tutorial.
    But when I want to set up automatic renewal of TLS certificate, I get the following error :

    chown www-data:www-data /var/www/html/ -R

    chown: invalid user: ‘www-data:www-data’

    Can you help me ? Please Thank you


    • Xiao Guoan (Admin)
      4 years ago

      The Nginx web server on CentOS runs as nginx user, not www-data user.

      • Raphael
        4 years ago


        Thanks to your help (relevant and quick response) I was able to finish the tutorial in a suitable way and in fact set up the automatic renewal of the certificate.

        Thank you


  • Raphael
    4 years ago


    By following your tutorial, do you install the Sogo part of the Iredmail application? Please thank you (If yes with which url do we connect to the Sogo management interface? Please thank you)

    If we don’t install Sogo, how can I install it so that it comes in addition to the Iredmail that I have just installed by following your tutorial?
    Thanks for this tutorial


    • Xiao Guoan (Admin)
      3 years ago

      The SOGo URL is

  • david chaganava
    3 years ago

    hello admin thenks for all.
    i whant my mail and web page was https how can do this?

  • Xiao, how can we increase upload size in Roundcube from default size of 10MB to 100MB for example.

    • Xiao Guoan (Admin)
      3 years ago

      To increase the upload size limit, edit the PHP configuration file.

      sudo nano /etc/php.ini

      Find the following line.

      upload_max_filesize = 10M

      Change the value like below. Note that this value should not be larger than the attachment size limit set by Postfix SMTP server.

      upload_max_filesize = 50M

      Then find the following line.

      post_max_size = 12M

      Change the maximum size of POST data that PHP will accept.

      post_max_size = 50M

      Save and close the file. Then restart PHP-FPM.

      sudo systemctl restart php-fpm

      Also edit the Roundcube config file.

      sudo nano /opt/www/roundcubemail/config/

      Find the following line and change it value.

      $config['max_message_size'] = '15M';

      Nginx also sets a limit of upload file size. Edit the following file.

      sudo nano /etc/nginx/conf-enabled/client_max_body_size.conf

      Change the default size

      client_max_body_size 12m;

      Save and close the file. Then reload Nginx for the changes to take effect.

      sudo systemctl reload nginx

      To change the attachment size limit in Postfix, run

      sudo postconf -e message_size_limit=51200000

      Then restart Postfix.

      sudo systemctl restart postfix
  • hi, everything was working great and went through the entire tutorial without any problems. but when i added the DKIM key and went back to the page i got a connection error page now where it wont load. Even my Roudcube url wont load and that was also working, right up until i added my DKIM DNS TXT record, now it wont load.

    I get this error:
    The connection has timed out

    An error occurred during a connection to

    The site could be temporarily unavailable or too busy. Try again in a few moments.
    If you are unable to load any pages, check your computer’s network connection.
    If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.

  • mixonic
    2 years ago

    It seems that iRedmail doesn’t work on Centos 8 anymore. When I try to install with wget command, I get an error:

    “Release version of the operating system on this server is unsupported by
    iRedMail, please access below link to get the latest iRedMail and a list
    of supported Linux/BSD distributions and release versions.”

    • mixonic
      2 years ago

      Yup, Centos 8 definitely is not supported anymore, but it works on Rocky Linux 8.5.

Leave a Comment

  • Comments with links are moderated by admin before published.
  • Your email address will not be published.
  • Use <pre> ... </pre> HTML tag to quote the output from your terminal/console.
  • Please use the community ( for questions unrelated to this article.
  • I don't have time to answer every question. Making a donation would incentivize me to spend more time answering questions.

The maximum upload file size: 2 MB. You can upload: image. Links to YouTube, Facebook, Twitter and other services inserted in the comment text will be automatically embedded. Drop file here