This tutorial will be showing you how to set up multiple email domains (virtual hosting) with Modoboa, which is an easy-to-use and open-source mail hosting solution. To follow this tutorial, it’s assumed that you have already set up a Modoboa mail server with one domain name.
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 the Modoboa admin panel.
- Create MX, A, SPF, DKIM and DMARC records for the new mail domain.
- Set up Webmail, Postfix and Dovecot for multiple domains
PTR record 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 Modoboa Admin Panel
Log into the Modoboa admin panel with the admin account. (https://mail.your-domain.com/admin
) Then go to Domains
tab and click Add
button to add a new domain.
Then enter your main domain name in the Name field. It is highly recommended that you enable DKIM signing, which can help with your domain reputation. In Key selector
filed, you can enter a random word like modoboa
. Choose 2048 as the key length.
In the next screen, you can choose to create an admin account for your domain. The SMTP protocol requires that a mail server should have a [email protected] address.
Click the Submit button and your new domain name will be added in Modoboa.
To add email addresses, go to Domains
tab and click your second domain name.
Then click mailboxes.
Click Add
button and choose Account
.
Then choose Simple user
as the role. Enter an email address in Username field and enter a password.
In the next screen, you can optionally create an alias for this email address.
After clicking the submit button, the email address is created.
Step 2: Creating MX, A, SPF, DKIM and DMARC record for the new mail domain
MX and A Record
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.
SPF, DKIM and DMARC 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
To create DKIM record, we need to get the public key. Go to Modoboa admin panel and select your second domain name in the Domains
tab. In the DNS section, click Show key
button.
The public key of the second domain will be revealed. There are two formats. We only need the Bind/named format.
Go to your DNS manager, create a TXT record, enter modoboa._domainkey
in the Name field. (Recall that we used modoboa as the selector when adding the second domain name in the admin panel.) Copy everything in the parentheses and paste into the value field. Delete all double quotes. Your DNS manager may require you to delete other invalid characters, such as carriage return.
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]
The above DMARC record is a safe starting point. To see the full explanation of DMARC, please check the following article.
Step 3: Setting up Webmail, 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 accessing webmail.
First, we need to add the second mail domain into the allowed hosts list. Edit the settings.py
file.
sudo nano /srv/modoboa/instance/instance/settings.py
Find the following lines.
ALLOWED_HOSTS = [
'mail.domain1.com',
]
Add your second domain.
ALLOWED_HOSTS = [ 'mail.domain1.com', 'mail.domain2.com', ]
Save and close the file. Then restart uWSGI for the change to take effect.
sudo systemctl restart uwsgi
Next, we need to create an Nginx virtual host file the second domain. Change working directory to /etc/nginx/sites-enabled
.
cd /etc/nginx/sites-enabled
Copy the content of the first mail domain virtual host file to the second domain virtual host file.
sudo cp mail.domain1.com.conf mail.domain2.com.conf
Edit the second domain virtual host file.
sudo nano mail.domain2.com.conf
Find the following line.
server_name mail.domain1.com;
We need to change the server_name to mail.domain2.com
server_name mail.domain2.com;
There are 2 instances of server_name
, you need to change both of them. (Note that you should not change the domain name in the SSL certificate path.) Then comment out the following 3 lines, because this upstream has already been defined in the mail.domain1.com.conf
file.
upstream modoboa { server unix:/run/uwsgi/app/modoboa_instance/socket fail_timeout=0; }
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 nginx 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 /opt/certbot-auto certonly --nginx --agree-tos -d mail.domain1.com,mail.domain2.com --cert-name mail.domain1.com --email your-email-address
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. Also note that we tell certbot to only obtain but not install the certificate (certonly).
When it asks if you want to update existing certificate to include the new domain, answer U and hit Enter.
Now you should see the following message, which indicates the multi-domain certificate is successfully obtained.
Reload Nginx to pick up the new certificate.
sudo systemctl reload nginx
You should now be able to use different domains to access 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 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. Choosenormal 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. Choosenormal password
as the authentication method.
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
Don’t forget to test your email score at https://www.mail-tester.com and also test email placement with GlockApps.
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 requires some time and effort, your emails will eventually be placed in the inbox after applying these tips.
(Optional) Set Up Autodiscover and AutoConfig for Multiple Domains
Autodiscover and AutoConfig make it easy to configure a desktop or mobile mail client. The end user just need to enter a name, email address and password to set up his/her mail account, without having to enter the SMTP or IMAP server details. Setting up Autodiscover and AutoConfig for multiple domains requires 2 simple steps.
First, create CNAME records for the second domain in your DNS manager,
autoconfig.domain2.com CNAME mail.domain2.com autodiscover.domain2.com CNAME mail.domain2.com
Then go to the Nginx virtual host directory.
cd /etc/nginx/sites-enabled/
Copy the autoconfig virtual host for the second domain.
sudo cp autoconfig.domain1.com.conf autoconfig.domain2.com.conf
Edit the new virtual host file.
sudo nano autoconfig.domain2.com.conf
Find the following line.
server_name autoconfig.domain1.com;
We need to change the server_name to autoconfig.domain2.com
server_name autoconfig.domain2.com;
Then comment out the following 3 lines, because this upstream has already been defined in the autoconfig.domain1.com.conf
file, we can’t define it again.
upstream automx { server unix:/run/uwsgi/app/automx_instance/socket fail_timeout=0; }
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 you can test the Autodiscover and AutoConfig feature in Microsoft Outlook and Mozilla Thunderbird mail client.
By default, AutoMX will send the first hostname (mail.domain1.com
) to mail clients who request Autodiscover and AutoConfig info, which means Microsoft Outlook and Mozilla Thunderbird would use mail.domain1.com
as the SMTP server and IMAP server for the second domain. This works, but isn’t perfect.
If you want Microsoft Outlook and Mozilla Thunderbird to use mail.domain2.com
as SMTP and IMAP server address for the second domain, then edit the AutoMX configuration file.
sudo nano /etc/automx.conf
Create a new section for the second domain at the end of this file.
[domain2.com]
Then copy the lines from the [global]
section and change the domain name.
[domain2.com] backend = sql action = settings account_type = email host = postgres://modoboa:[email protected]/modoboa query = SELECT first_name || ' ' || last_name AS display_name, email, SPLIT_PART(email, '@', 2) AS domain FROM core_user WHERE email='%s' AND is_active result_attrs = display_name, email smtp = yes smtp_server = mail.domain2.com smtp_port = 587 smtp_encryption = starttls smtp_auth = plaintext smtp_auth_identity = ${email} smtp_refresh_ttl = 6 smtp_default = yes imap = yes imap_server = mail.domain2.com imap_port = 143 imap_encryption = starttls imap_auth = plaintext imap_auth_identity = ${email} imap_refresh_ttl = 6 pop = yes pop_server = mail.domain2.com pop_port = 110 pop_encryption = starttls pop_auth = plaintext pop_auth_identity = ${email}
Save and close the file. Then restart AutoMX.
sudo systemctl restart uwsgi
Wrapping Up
That’s it! I hope this tutorial helped you host multiple email domains with Modoboa. 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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