What is this?

A simple, quick way to deploy a dockerized mail server (SMTP/IMAP) based on postfix and dovecot and managed via ViMbAdmin. If you just want to make things work without building anything locally, here's the Docker Hub repository.

Key features

The main goal of this project is to offer a complete dockerized IMAP/SMTP server which supports virtual mailboxes, aliases, quotas, etc, and a GUI to manage it all.

The following table serves as a summary of the current state of things:

Component	Status
IMAP server (Dovecot)	Working
SMTP server (Postfix)	Working
Web administration (ViMbAdmin)	Working
Spam blocker (SpamAssassin)	Planned
Webmail client	Future

Prerequisites

• I assume you know about SPF, DKIM and DMARC. If you don't, you should check out any online guide about it. You will need to place TXT records in your DNS for SPF, DMARC and DKIM, so everybody takes you seriously and your emails are not marked as spam. If you are in a hurry, you can just fill the templates I provide in section DNS records.

Tested architectures

Architecture	Status
amd64	Working
arm64	Working
arm32	Failing*

* There is no mysql/mariadb official docker image for ARMv7 systems. Also, ubuntu:latest have issues with this architecture. Nonetheless, I may consider working on a build for this architecture if requested.

Building locally

If you wish to build all containers locally, you may do that as well. Just follow these steps:

1. Ensure you have docker and docker-compose installed in your system.
2. Checkout this repository (or download a release).
3. Enter the root folder of the project.
4. Create your secrets files. You can follow the sample structure of docker-compose.yaml.
5. Modify docker-compose.yaml and mail.env files according to your secrets files and your own particular scenario (volumes to mount, certificates, etc).
6. Run docker-compose up -d.

Environment variables

You will need to create two .env files in the same directory where docker-compose.yaml file is located: db.env and mail.env.

The following table explains the variables to be filled in db.env file:

Variable	Explanation
MYSQL_ROOT_PASSWORD_FILE	The path to the file containing the password for the root user of the mysql/mariadb database.
MYSQL_DATABASE_FILE	The path to the file containing the name of the database to be used by ViMbAdmin. Currently, it needs to be vimbadmin.
MYSQL_USER_FILE	The path to the file containing the name of the mysql user to be used by ViMbadmin.
MYSQL_PASSWORD_FILE	The path to the file containing password of the mysql user to be used by ViMbAdmin.

And the following table shows the variables to be filled in mail.env:

Variable	Explanation
DOMAIN_NAME	Your domain name: something like example.com.

Note that all enviromental variables must be filled.

Secrets

The approach used for protecting sensitive information in this project is Docker Secrets, as you can see in the docker-compose template provided above. Using secrets is almost as easy as using environmental variables, just more safe. For instance, instead of directly setting the password for the ViMbAdmin mysql user via MYSQL_PASSWORD environmental variable, we use a variable (MYSQL_PASSWORD_FILE) that contains the path of the password, but not the password itself. The docker-compose template includes some comments to help you understand how to use these secrets, but, basically you will need to:

1. Create a secrets folder in the same directory where docker-compose.yaml is located.
2. Create a txtfile inside the secrets' folder for each environment variable in db.env.
3. Reference those files in docker-compose.yaml.

Configuration files and mail directory

Configuration files are stored, by default, inside /srv/mailserver in this way: Postfix's files are stored in /srv/mailserver/postfix, Dovecot's files are stored in /srv/mailserver/dovecot, and so on. Of course, you can change this whenever you want.

The mail directory or maildir is stored inside /srv/mailserver by default. For instance, you will find the files for hello@example.com in /srv/mailserver/maildir/example.com/hello.

The archive folder is disabled by default in the dovecot configuration, but can be easily enabled by just uncommenting it in 10-mail.conf. Moreover, the default quota is set to 1GB (can be overwritten by ViMbAdmin), and the maximun email size is set to 50MB.

Logging

You can check the docker logs anytime by using docker logs <container-name>, but in case you need more detailed information:

• ViMbAdmin logs to /srv/mailserver/var/log/vimbadmin.log by default.
• Postfix and OpenDKIM log to /var/log/syslog by default, since /dev/log is mounted for both containers.
• Dovecot logs to several files inside /srv/mailserver/dovecot/logs by default.

Customization

You may change anything you want, of course, but have in mind that:

• Changing MySQL credentials will only affect the containers which query the database container, not the database container itself. To prevent problems, make sure you update the database container's credentials as well.

• Changing the domain name will probably lead to update all SSL files so that they match the new domain.

DNS records

You will need to place TXT records in your DNS for SPF, DMARC and DKIM, so everybody likes your emails and they are not marked as spam.

In case you are in a hurry, I provide a template for every record so you can just fill them up and upload them. However, I recommend doing a little research to make your records fit your exact needings.

SPF

You can make the TXT entry example.com return

v=spf1 mx a ~all

DKIM

You can make the TXT entry mail._domainkey.example.com return

v=DKIM1;h=sha256;k=rsa;t=y;p=<dkim_public_key>

DMARC

You can make the TXT entry _dmarc.example.com return

v=DMARC1; adkim=r; pct=100; rf=afrf; fo=1;p=quarantine; rua=mailto:admin@example.com; ruf=mailto:admin@example.com;

Known issues

• If you want to use a reverse proxy for ViMbAdmin and run the ViMbAdmin container with no TLS, that's fine, but keep in mind that the website's content may not be displayed correctly in modern browsers, since you'd be asking for JS and CSS resources via HTTP, and the browser will most likely block the requests, even though your reverse proxy redirects those requests to the HTTPS endpoint.

Troubleshooting

If you deploy this scenario and something does not work, try the following:

• Check that your SSL files are where they are supposed to be. If they are not where the docker-compose.yaml says they are, docker will just create empty files or folders there.
• Check your DNS records: something might not be in place (SPF, DMARC, DKIM, A records pointing to the mailserver...).
• Check your firewall rules and ensure all redirected ports are accessible.
• Check the logs: it is possible that I missed something (I'm only human).

Notes

• Even though this should provide a good starting point, you may want to do some research and adjust parameters to better fit your own needs. Feel free to try and experiment!
• Special thanks to ViMbadmin developers: their project inspired me to do this.