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https://github.com/xrstf/mail-o-rama

Super simple mail server in Docker
https://github.com/xrstf/mail-o-rama

debian dkimproxy docker dovecot imap opensmtpd

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Super simple mail server in Docker

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README 

        
# Mail-o-Rama



This is a very simple mail server based on Docker with these features:



* Multiple mail accounts

* Multiple virtual e-mail addresses per account

* SMTP via OpenSMTPD

* IMAP via Dovecot

* DKIM signatures via dkimproxy



Mail-o-Rama is useful for smaller personal e-mail setups. I wrote thise because

the existing alternatives are just not my taste:



* poste.io does not play well when you have an existing Let's Encrypt setup.

* mailcow uses too many containers and has "too many features" for my taste.



There are many other solutions out there, but this one is mine. It does **not**

feature the following:



* **NO** spam filter (though this might change at some point)

* **NO** virus scanner

* **NO** webmailer

* **NO** management UI

* **NO** SQL databases



## Usage



For running the Docker container, you need a couple of text files.



### `accounts`



This file should contain a list of your accounts, one per line. For each account,

you have to spcify a name, a user ID and a password hash. This is very similar

to regular UNIX user information and in fact, this is (also) used to setup system

accounts within the container.



    al    1000 $6$OxCmLiR/Ynm....

    peggy 1001 $6$OxCmLiR/Ynm....

    kelly 1002 $6$OxCmLiR/Ynm....



Make sure to never rename or re-number the accounts without also taking care of

the existing mail data.



### `domains`



This file contains a list of all the domains you want to handle e-mail for, for

example



    bundy.net

    example.com

    chicago.com



You can add or remove domains at any point, this should not affect existing

e-mails.



### `virtuals`



This is the "meat" of your configuration: the list of all existing e-mail

addresses. Each line contains a mapping of e-mail address to one or more user

accounts or external addresses. Separate targets by comma:



    [email protected]       al

    [email protected]     al

    [email protected]     al

    [email protected]    peggy

    [email protected]      [email protected]

    [email protected]   al,peggy,[email protected]



You can manage this file as you like, it should not affect existing mail data.



### `aliases`



This file defines aliases for system accounts. You will probably rarely get

mails from within your container, but this file is used when you relay mails

from the Docker host system into your container (see below).



    root:al

    pumpkin:kelly



### Running the container



See the `docker-compose.yml` file for usage instructions.



## Local System Mail



The goal is to get rid of as much e-mail infrastructure on the host system as

possible. But this leaves the question as to how mails from your cron daemon

reaches your inbox. You have basically two options:



### SMTP-based using an MTA



You can install a classic MTA like sendmail, postfix or exim on your Docker host

and configure it to relay mail to the Docker container via SMTP. This has the

drawback that you need to map your host usernames to e-mail addresses (because

you cannot send an e-mail just to "root"), but at the same time is the only

viable solution when you have other Docker containers that also should send

e-mail.



An easy solution is to use `msmtp`. In many cases (like for Archlinux and Debian)

there's an addtional package, `msmtp-mta`, that provides a `/usr/sbin/sendmail`

program. A sample configuration could look like this:



    # Set default values for all following accounts.

    defaults

    aliases   /etc/aliases.msmtp



    # Mail-o-Rama

    account   mailorama

    host      localhost

    port      25

    from      [email protected]



    # Set a default account

    account default : mailorama



You also want to have an aliases file that maps your user accounts to an e-mail

address. The regular `/etc/aliases` does not work if it contains mappings for

non-existing users, so it's probably a good idea to use a dedicated aliases file

that looks like this:



    root: [email protected]

    al: [email protected]



It should be very easy to install an MTA like this into your other Docker

containers to have them also properly deliver their mail to you.



### Use `docker exec` and sendmail



Instead of sending e-mail via SMTP to the container, you can also use the

sendmail aliases that's provided by OpenSMTPD. For this, you need something on

your host that runs `docker exec -i  sendmail ...` for each new

mail. In this case, usernames are mappened to mail accounts using the

`/etc/aliases` file *inside the container*.



The `/usr/sbin/sendmail` program cannot be a shellscript, because programs like

cron run it via `popen()`. To work around this, I wrote a very simple Go program

that can be used as your local sendmail program. See the `sendmail/` directory

for the source and some precompiled binaries. Simply place the binary at

`/usr/sbin/sendmail` (or symlink it) and make sure to configure the container

name



* either by setting a system-wide environment variable

  `MAILORAMA_CONTAINER=`

* or by creating an INI file in `/etc/mail-o-rama/sendmail.ini` with only one

  setting: `container = `



## Backups



As e-mail data is stored in Maildirs, creating a backup can be as simple as

`tar`ing up each mail account. To make things simpler, there is a tiny

`backup.sh` script included in the image which is meant to be called once per

day via



    docker-compose exec mail-o-rama /backup.sh



The script will create tar.gz files (named as ``YYYY-MM-DD.tar.gz``) in each

mail account directory. If you set the `BACKUP_RETENTION_DAYS` environment

variable to a non-empty value, the script will also cleanup old backups

automatically.