How to Host Multiple Mail Domains in iRedMail with Nginx

This tutorial will be showing you how to set up multiple email domains with iRedMail, which is an easy way to set up your own email server.

Prerequisites

To follow this tutorial, it’s assumed that

What You Need to Do

If you want to host multiple mail domains, then you need to

  • Add a new mail domain and user in iRedMail admin panel.
  • Create MX, A and SPF record for the new mail domain.
  • Set up DKIM signing for additional domains
  • Set up DMARC Record for the new domain.
  • Set up RoundCube Webmail, Postfix and Dovecot for multiple domains
Reverse DNS check is used to check if the sender’s IP address matches the HELO hostname. You don’t need to add another PTR record when adding a new mail domain.

Step 1: Adding Additional Domains in iRedMail Admin Panel

Log into iRedMail admin panel with the postmaster account. (https://mail.your-domain.com/iredadmin) Then add domains in the Add tab.

iredmail multiple domains

Next, add a user under the new domain.

iredmail multiple domains ssl

Step 2: Creating MX, A and SPF record for the new mail domain

In your DNS manager, add MX record for the new domain like below.

Record Type    Name      Value

MX             @         mail.domain2.com

The A record points to your mail server’s IP address.

Record Type    Name     Value

A              mail     IP-address-of-mail-server

If your server uses IPv6 address, be sure to add AAAA record.

Then create SPF record to allow the MX host to send email for the new mail domain.

Record Type    Name      Value

TXT            @         v=spf1 mx ~all

Step 3: Setting up DKIM signing for the new domain

You need to tell amavisd to sign every outgoing email for the new mail domain. Edit /etc/amavis/conf.d/50-user file.

sudo nano /etc/amavis/conf.d/50-user

Find the following line,

dkim_key('domain1.com', 'dkim', '/var/lib/dkim/domain1.com.pem');

Add another line to specify the location of the private key of second domain.

dkim_key('domain2.com', 'dkim', '/var/lib/dkim/domain2.com.pem');

In @dkim_signature_options_bysender_maps section, add the following line.

 "domain2.com" => { d => "domain2.com", a => 'rsa-sha256', ttl => 10*24*3600 },

amavis dkim signing

Save and close the file. Then generate the private key for the second domain.

sudo amavisd-new genrsa /var/lib/dkim/domain2.com.pem 2048

Restart Amavis.

sudo systemctl restart amavis

Display the public keys.

sudo amavisd-new showkeys

All public keys will be displayed. We need the public key of the second domain, which is in the parentheses.

amavis show keys

In your DNS manager, create a TXT record for the second domain. Enter dkim._domainkey in the Name field. Copy everything in the parentheses and paste into the value field. Delete all double quotes. (You can paste it into a text editor first, delete all double quotes, the copy it to your DNS manager. Your DNS manager may require you to delete other invalid characters, such as carriage return.)

amavisd-new ubuntu

After saving your changes. Check the TXT record with this command.

dig TXT dkim._domainkey.domain2.com

Now you can run the following command to test if your DKIM DNS record is correct.

sudo amavisd-new testkeys

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

TESTING#1 domain1.com: dkim._domainkey.domain1.com => pass
TESTING#2 domain2.com: dkim._domainkey.domain2.com => pass

Step4: Setting Up DMARC Record For the New Domain

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:

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

create dmarc record txt

The above DMARC record is a safe starting point. To see the full explanation of DMARC, please check the following article.

Step 5: Setting up RoundCube, Postfix and Dovecot for Multiple Domains

It makes sense to let users of the first domain use mail.domain1.com and users of the second domain use mail.domain2.com when using RoundCube webmail.

Change working directory to /etc/nginx/.

cd /etc/nginx/

Create a blank server block file for the second domain in /etc/nginx/sites-enabled/ directory.

sudo touch sites-enabled/mail.domain2.com.conf

Copy the default HTTP site configurations to the file.

cat sites-enabled/00-default.conf | sudo tee -a sites-enabled/mail.domain2.com.conf

Copy the default SSL site configurations to the file.

cat sites-enabled/00-default-ssl.conf | sudo tee -a sites-enabled/mail.domain2.com.conf

Edit the virtual host file.

sudo nano sites-enabled/mail.domain2.com.conf

Find the following line.

server_name _;

We need to change the server_name to mail.domain2.com, because later we need to use Certbot to generate a new tls certificate.

server_name mail.domain2.com;

There are 2 instances of server_name, you need to change both of them. Save and close the file. Then test Nginx configuartion.

sudo nginx -t

If the test is successful, reload Nginx for the changes to take effect.

sudo systemctl reload nginx

Now use Certbot webroot plugin to obtain TLS certificate for all your mail domains, so you will have a single TLS certificate with multiple domain names on it.

sudo certbot certonly --webroot --agree-tos -d mail.domain1.com,mail.domain2.com --cert-name mail.domain1.com --email your-email-address -w /var/www/html

Notice that in the above command, we specified the cert name using the first mail domain, which will be used in the file path, so you don’t have to change the file path in Postfix or Dovecot configuration file.

When it asks if you want to update existing certificate to include the new domain, answer U and hit Enter.

certbot multi-domain iredmail

Now you should see the following message, which indicates the multi-domain certificate is successfully obtained.

iredmail nginx multiple domain

Reload Nginx to pick up the new certificate.

sudo systemctl reload nginx

You should now be able to use different domains to access RoundCube webmail. Also you need to reload Postfix SMTP server and Dovecot IMAP server in order to let them pick up the new certificate.

sudo systemctl reload postfix

sudo systemctl reload dovecot

Using Mail Client on Your Computer or Mobile Device

Fire up your desktop email client such as Mozilla Thunderbird and add a mail account of the second domain.

  • In the incoming server section, select IMAP protocol, enter mail.domain2.com as the server name, choose port 993 and SSL/TLS. Choose normal password as the authentication method.
  • In the outgoing section, select SMTP protocol, enter mail.domain2.com as the server name, choose port 587 and STARTTLS. Choose normal password as the authentication method.

iredmail multiple domain postfix dovecot

Although Postfix SMTP server and Dovecot IMAP server are using the hostname of the first mail domain (mail.domain1.com) when communicating with others, they are now using a multi-domain certificate, so the mail client won’t display certificate warnings.

SPF and DKIM Check

Now you can use your desktop email client or webmail client to send a test email to [email protected] and get a free email authentication report. Here’s the report I got from port25.com

postfix spf dkim ubuntu

Don’t forget to test your email score at https://www.mail-tester.com and also GlockApps.com.

That’s it! I hope this tutorial helped you host multiple email domains with iRedMail. As always, if you found this post useful, then subscribe to our free newsletter to get more tips and tricks. Take care 🙂

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18 Responses to “How to Host Multiple Mail Domains in iRedMail with Nginx

  • Thank you for this interesting read.
    Is there any encryption implemented for mail data stored at the server?
    If not, how would I add this?

  • You’re tutorials are great, I have been following a few of them.

    Right now I have a problem, when trying to setup a second domain like in this tutorial.
    My second domain can send mails without a problem, but it does not receive any email.
    The strange thing is, that the sender also does not get an error message. The mail just disappears and is neither delivered nor rejected.

    DNS settings are all correct. I do not know where else to look.

    Thanks for helping

    • You should check the mail log (/var/log/mail.log) on the receiving email server. If DNS records are correct, you will see the sender in the mail log and it will tell you the reason why the email wasn’t delivered.

  • Hi Xiao,
    that definitely gives me more info about the problem. It seems that all mails send to this domain are queued indefinitely

    Dec  1 22:18:14 mail postfix/postscreen[10894]: PASS NEW [209.85.214.178]:44948
    Dec  1 22:18:14 mail postfix/smtpd[10902]: connect from mail-pl1-f178.google.com[209.85.214.178]
    Dec  1 22:18:14 mail postfix/smtpd[10902]: Anonymous TLS connection established from mail-pl1-f178.google.com[209.85.214.178]: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
    Dec  1 22:18:15 mail postfix/smtpd[10902]: 28E18414F8: client=mail-pl1-f178.google.com[209.85.214.178]
    Dec  1 22:18:15 mail postfix/cleanup[10911]: 28E18414F8: message-id=
    Dec  1 22:18:15 mail postfix/qmgr[10781]: 28E18414F8: from=, size=2777, nrcpt=1 (queue active)
    Dec  1 22:18:15 mail postfix/smtpd[10902]: disconnect from mail-pl1-f178.google.com[209.85.214.178] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7
    

    I do not know why this happens.

    I restarted amavis and nginx and now it is working. This seems strange.
    Thanks

    Really appreciate your tutorials! 5 out of 5

  • Dave Kimble
    5 months ago

    The only weakness of iRedMail is that if it fails to install correctly, or gets corrupted later, they recommend reinstalling the OS then iRedMail again. This wouldn’t be necessary if they kept a strict log of all the changes made with the location, old-value and new-value, so that “apt purge” could use the log to undo all changes.

  • Hi Xiao,
    I set up the mail-server with iRedMail on Ubuntu 16.04 for one domain without any problems. Your guide is great.
    But I try to set up multiple domains and problems start.
    Can not set up dkim._domainkey in my DNS zone. I get a message: “The hostname of the record does not match the name of the zone.”
    The main domain (mydomain.com) is pointed to a different IP address than the mail subdomain (mail.domain.com).
    I have website on other VPS than mail-server. How to fix it?
    In my DNS zone I have:
    mydomain.com | A | IP 1 (111.111.11.11)
    www.mydomain.com | CNAME | mydomain.com
    mail.mydomain.com | A | IP 2 (222.222.22.22)
    mydomain.com | MX | 10 | mail.mydomain.com
    mydomain.com | TXT | v=spf1 mx ~all

    • OK – I fixed it. The question from the previous comment is out of date.
      Everything working fine with two domains and different IP addresses.
      Score 10/10 for both domains.
      Thank you again for great tutorials.

    • Glad to know it’s working for you now 🙂

  • Fantastic job! It is nice to see a tutorial which actually works! Most of these kind of tutorials have a ton of errors and they don’t work exactly right so you have to do a lot of digging on your own. Yours are spot on!

    This got me up and running perfectly. The only gap I have now is how to configure and administer the spam components and whitelists/blacklists for iRedMail. Do you have a tutorial on that or can you recommend a good resource?

    • iRedMail uses Postscreen and SpamAssassin for spam filtering, which is configured in /etc/postfix/main.cf file. Another good tool is rspamd, which has a nice web-based graphical interface. I will write an article about rspamd.

      • Thank you! I am really looking forward to that! I know iRedMail uses Amavised-new, SpamAssassin & ClamAV. Are these (or suitable replacements) integrated into rspamd so we only have one interface to deal with for virus filtering, spam and whitelists/blacklists? Or do I need to look at other solutions for some of that? I glanced at rspamd.com really quickly but couldn’t tell what components they are using. Thank you again for everything. I will be donating to support the site!

  • tom_cr00z
    4 months ago

    clarification in order this to work i have to get another domain right and point with the same public ip address of my current iredmail server?

    • I suppose that you asked “The A record for mail.domain2.com should be pointed to the public IP address of the current iRedMail server?”

      The answer is Yes.

  • tom_cr00z
    4 months ago

    your the best bro

  • Hello Xiao, you mentioned in another post that it was possible to run other sites alongside this setup. How can this be done? I had it working previously, but I have no idea how I did it. Any tips? Thanks.

  • Hello Xiao,

    i see that you want to write an article about rspamd, it is possible to do it with a howto for switching from amavis(spamassasin) to rspamd I. iredmail?

    Thx

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