Merge branch 'master' into terminal
This commit is contained in:
commit
fdfbb65634
GPG key ID:
3F257B68F5BC9339
3 changed files with 280 additions and 3 deletions
274
content/blog/mail_server_alpine_postfix_dovecot_tutorial.md
Normal file
274
content/blog/mail_server_alpine_postfix_dovecot_tutorial.md
Normal file
|
|
@ -0,0 +1,274 @@
|
||||||
|
+++
|
||||||
|
date = '2024-11-19T16:29:01Z'
|
||||||
|
draft = true
|
||||||
|
title = 'How to Set up a Mail Server on Alpine Linux with Postfix and Dovecot'
|
||||||
|
+++
|
||||||
|
|
||||||
|
# About mail servers
|
||||||
|
|
||||||
|
Simply put, a mail server sends and receives email. When `ruby@protonmail.com` emails `klaasje@gmail.com`, Protonmail's
|
||||||
|
mail server's <abbr title="Mail Transfer Agent">MTA</abbr> sends the email to Google's mail server's MTA. Google's
|
||||||
|
MTA then passes the email on to Google's <abbr title="Mail Delivery Agent">MDA</abbr>, which is responsible for storing
|
||||||
|
the email. MDAs also run <abbr title="Internet Message Access Protocol">IMAP</abbr> or <abbr
|
||||||
|
title="Post Office Protocol 3">POP3</abbr> servers so you can read your emails and send emails with an email client.
|
||||||
|
IMAP and POP3 are protocols for email retrieval over [TCP/IP](https://en.wikipedia.org/wiki/Internet_protocol_suite).
|
||||||
|
For sending email, you would use [<abbr
|
||||||
|
title="Simple Mail Transfer Protocol">SMTP</abbr>](https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol).
|
||||||
|
|
||||||
|
Or visualise it like this:
|
||||||
|
|
||||||
|
Ruby's email client via SMTP -> Protonmail's MTA -> Google's MTA -> Google's MDA -> Klaasje's email client via IMAP
|
||||||
|
|
||||||
|
A mail server is software which can be run on any computer, including yours. You can host a mail server on a server you
|
||||||
|
already own that is hosting other services, so long as those other services aren't using any of the [mail
|
||||||
|
ports](## Unblock your ports).
|
||||||
|
|
||||||
|
# Why this tutorial?
|
||||||
|
|
||||||
|
There are many tutorials on the internet about how to set up a mail server. I don't claim that mine is particularly
|
||||||
|
better than anyone else's; I'm mostly writing this for my own reference so that I can recreate my own setup on new
|
||||||
|
machines.
|
||||||
|
|
||||||
|
There are existing
|
||||||
|
[mail server tutorials for Alpine Linux](https://wiki.alpinelinux.org/wiki/Hosting_services_on_Alpine#Mail), including
|
||||||
|
ones for Postfix and Dovecot. This tutorial aims to be "monolithic" (i.e. covers the entire mail server setup with all
|
||||||
|
its components), making it easier to follow without trying to follow different tutorials that may not be 100%
|
||||||
|
compatible with each other, and to be adapted to my own specific use-cases, which may not be yours.
|
||||||
|
|
||||||
|
I am hugely indebted to [LinuxBabe's mail server tutorial for
|
||||||
|
Ubuntu](https://www.linuxbabe.com/mail-server/setup-basic-postfix-mail-sever-ubuntu), which is actually what I followed
|
||||||
|
to set up my own server. Essentially, this tutorial could be thought of as an Alpine Linux adaptation of LinuxBabe's
|
||||||
|
tutorial. If you want to set up an Ubuntu or Debian mail server, I recommend following LinuxBabe's tutorial, which is
|
||||||
|
written very clearly and is easy to follow.
|
||||||
|
|
||||||
|
The mail server will be composed of the following software:
|
||||||
|
|
||||||
|
<!-- Using an html table for colspan & rowspan -->
|
||||||
|
<table>
|
||||||
|
<tr>
|
||||||
|
<th>Component</th>
|
||||||
|
<th colspan="2">Software</th>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td>Mail transfer agent</td>
|
||||||
|
<td colspan="2">Postfix</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td>Mail delivery agent</td>
|
||||||
|
<td colspan="2">DKIM authentication and signing</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td>Spam filter</td>
|
||||||
|
<td rowspan="2">Amavis</td>
|
||||||
|
<td>SpamAssassin</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td>Antivirus</td>
|
||||||
|
<td>ClamAV</td>
|
||||||
|
</tr>
|
||||||
|
<tr>
|
||||||
|
<td>MDA server-side filtering</td>
|
||||||
|
<td colspan="2">Pigeonhole</td>
|
||||||
|
</tr>
|
||||||
|
</table>
|
||||||
|
|
||||||
|
Postfix will be our SMTP server, and Dovecot will run an IMAP server for us.
|
||||||
|
|
||||||
|
Postfix and Dovecot are required for the minimum of what you'd expect from a working mail server (i.e. a user can log
|
||||||
|
in through a standard SMTP/IMAP/POP3 email client, read their emails, and send emails). The rest is optional and
|
||||||
|
modular, i.e. you can opt to have e.g. Pigeonhole but not Amavis.
|
||||||
|
|
||||||
|
We will end up with a small-scale mail server running on Alpine Linux with one domain, and we will use Unix user
|
||||||
|
accounts as mail accounts.
|
||||||
|
|
||||||
|
This tutorial was written for Alpine Linux 3.20.3, though will most likely work on other versions too.
|
||||||
|
|
||||||
|
This tutorial assumes no prior knowledge about mail servers.
|
||||||
|
|
||||||
|
# You will need
|
||||||
|
|
||||||
|
## A server
|
||||||
|
|
||||||
|
Any computer will do. This tutorial is for Alpine Linux specifically.
|
||||||
|
|
||||||
|
The relevant thing to consider for your server is that port 25 (the port for sending email) is not blocked. Most <abbr
|
||||||
|
title="Virtual Private Server">VPS</abbr> hosts block port 25 because spammers commonly use VPSes to send spam, so you
|
||||||
|
will need to find one that doesn't block port 25. Some VPS hosts block port 25 by default, but will unblock it upon
|
||||||
|
request, and re-block it if they find you are spamming.
|
||||||
|
|
||||||
|
## A domain name
|
||||||
|
|
||||||
|
Self-explanatory. You need a domain name and the ability to set its DNS records.
|
||||||
|
|
||||||
|
# Before you start
|
||||||
|
|
||||||
|
## Set up your DNS records
|
||||||
|
|
||||||
|
Firstly, pick a domain for your mail server. If you're sending emails from `domain.com`, `mail.domain.com` is a common
|
||||||
|
choice.
|
||||||
|
|
||||||
|
### MX record
|
||||||
|
|
||||||
|
An MX record denotes that your domain is used to send and receive email, and tells other MTAs the domain name of your
|
||||||
|
mail server. We will use `mail.domain.com` for your MX record. For instance, my MX record looks like:
|
||||||
|
|
||||||
|
```bindzone
|
||||||
|
revsuine.xyz. 14400 IN MX 0 mail.revsuine.xyz
|
||||||
|
```
|
||||||
|
|
||||||
|
### Mail server records (A, AAAA, and/or CNAME)
|
||||||
|
|
||||||
|
Now you need to set a record stating the IP address of your mail server (`mail.domain.com` above). Depending on your
|
||||||
|
setup, you may want to create a CNAME record pointing to `domain.com` if the IP address of `mail.domain.com` is the
|
||||||
|
same as the IP address of `domain.com`, or an A record if the IP address is not shared with another domain.
|
||||||
|
|
||||||
|
I use a CNAME record because the IP addresses of `mail.revsuine.xyz` and `revsuine.xyz` are the same, so my record is:
|
||||||
|
|
||||||
|
```bindzone
|
||||||
|
mail.revsuine.xyz. 14400 IN CNAME revsuine.xyz
|
||||||
|
```
|
||||||
|
|
||||||
|
If you use an A record, your record may look something like
|
||||||
|
|
||||||
|
```bindzone
|
||||||
|
mail.domain.com. 14400 IN A ip.address.here
|
||||||
|
```
|
||||||
|
|
||||||
|
If you use IPv6, you should also add an AAAA record, e.g.:
|
||||||
|
|
||||||
|
```bindzone
|
||||||
|
mail.domain.com. 14400 IN AAAA ip:address:here::
|
||||||
|
```
|
||||||
|
|
||||||
|
### A note on my DNS records
|
||||||
|
|
||||||
|
I use one server with one IP address for hosting several services under one apex domain. For instance, my static
|
||||||
|
website is hosted at `revsuine.xyz`; my Nextcloud is hosted at `cloud.revsuine.xyz`; and my mail server is hosted at
|
||||||
|
`mail.revsuine.xyz`. To handle this setup, I've created a subdomain `master.revsuine.xyz` (you can call the subdomain
|
||||||
|
anything you want) with an *A record* (because your [PTR record](### PTR record) is expected to be an A record, not a
|
||||||
|
CNAME record) to my server's IP address.
|
||||||
|
|
||||||
|
I set my server's hostname and PTR record to `master.revsuine.xyz`. I will also refer to this `master.revsuine.xyz`
|
||||||
|
subdomain further down when configuring Postfix.
|
||||||
|
|
||||||
|
### PTR record
|
||||||
|
|
||||||
|
A PTR record is used for "reverse DNS", or rDNS, lookup: instead of mapping a domain to an IP address, it maps an IP
|
||||||
|
address to a domain. It is not managed through your DNS manager (e.g. whomever you bought your domain name from), but
|
||||||
|
through whoever gives you your IP address. If you rent a server, be it a VPS or a dedicated server, your hosting
|
||||||
|
provider whom you rent from will be able to manage PTR records. You may have an option to add a PTR record in the
|
||||||
|
dashboard of your hosting provider, or you may have to contact their support to get a PTR record added.
|
||||||
|
|
||||||
|
For the above stated reasons, my PTR record for my single server (which hosts all my services) is `master.revsuine.xyz`.
|
||||||
|
|
||||||
|
If your hostname is `mail.domain.com`, your PTR record should be `mail.domain.com`.
|
||||||
|
|
||||||
|
## Unblock your ports
|
||||||
|
|
||||||
|
After unblocking ports from your internet provider (e.g. if your VPS host blocks outgoing port 25), make sure the
|
||||||
|
following TCP ports are open on your firewall:
|
||||||
|
|
||||||
|
| Port | Usage |
|
||||||
|
| ---- | --------------------------------- |
|
||||||
|
| 25 | SMTP |
|
||||||
|
| 143 | IMAP |
|
||||||
|
| 465 | Email message submission over TLS |
|
||||||
|
| 587 | Email message submission |
|
||||||
|
| 993 | IMAPS (IMAP over TLS) |
|
||||||
|
|
||||||
|
# Postfix
|
||||||
|
|
||||||
|
Postfix is a [mail transport agent](https://en.wikipedia.org/wiki/Message_transfer_agent) (aka SMTP server). [In its
|
||||||
|
own words](https://www.postfix.org/):
|
||||||
|
|
||||||
|
> Postfix attempts to be fast, easy to administer, and secure. The outside has a definite Sendmail-ish flavor, but the
|
||||||
|
> inside is completely different.
|
||||||
|
|
||||||
|
## Installing Postfix
|
||||||
|
|
||||||
|
On your server, install Postfix with:
|
||||||
|
|
||||||
|
# apk add postfix
|
||||||
|
|
||||||
|
You likely also want to have Postfix documentation:
|
||||||
|
|
||||||
|
# apk add postfix-doc
|
||||||
|
|
||||||
|
Verify that Postfix is installed by checking its version:
|
||||||
|
|
||||||
|
$ postconf mail_version
|
||||||
|
|
||||||
|
## Configuring Postfix
|
||||||
|
|
||||||
|
Edit `/etc/postfix/main.cf`.
|
||||||
|
|
||||||
|
You should set `myhostname` to the hostname of your server; [in my case, this is
|
||||||
|
`master.revsuine.xyz`](### A note on my DNS records).
|
||||||
|
|
||||||
|
Now set `mydomain` to the domain you intend to send email from. For instance, my email addresses are
|
||||||
|
`name@revsuine.xyz`, so `mydomain` is set to `revsuine.xyz`.
|
||||||
|
|
||||||
|
`myorigin` determines the domain name in the `From:` field of locally sent emails. So you could for instance set this
|
||||||
|
to `revsuine.xyz`.
|
||||||
|
|
||||||
|
`maillog_file` denotes where Postfix's log file is. By default this is `/var/log/messages`; you may want to configure
|
||||||
|
Postfix to have a dedicated log file like `/var/log/postfix.log`.
|
||||||
|
|
||||||
|
You probably want to have `logrotate` rotate your Postfix log. If there isn't already such a file, you want to create
|
||||||
|
one at `/etc/logrotate.d/postfix`:
|
||||||
|
|
||||||
|
```
|
||||||
|
/var/log/postfix*.log
|
||||||
|
/var/log/mail*.log
|
||||||
|
{
|
||||||
|
daily
|
||||||
|
missingok
|
||||||
|
notifempty
|
||||||
|
rotate 7
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
## Send your first email
|
||||||
|
|
||||||
|
Have the `postfix` service auto-start upon boot, and start it during this session:
|
||||||
|
|
||||||
|
# rc-update add postfix default
|
||||||
|
# rc-service postfix start
|
||||||
|
|
||||||
|
You can now send an email with the following command:
|
||||||
|
|
||||||
|
$ echo "test email" | sendmail user@externaldomain.com
|
||||||
|
|
||||||
|
Send this email to your email account with an external server, e.g. a gmail account. Note that Protonmail has quite
|
||||||
|
stringent spam filters and this likely would be rejected by Protonmail, i.e. not even reach your spam folder.
|
||||||
|
|
||||||
|
## Configure email aliases
|
||||||
|
|
||||||
|
You can configure aliases for your mail server. Edit the `/etc/postfix/aliases`[^postfix_aliases_location] file.
|
||||||
|
|
||||||
|
You shouldn't receive mail as root, so configure `root` to have an alias to your user, e.g.
|
||||||
|
|
||||||
|
```
|
||||||
|
root: revsuine
|
||||||
|
```
|
||||||
|
|
||||||
|
You also *must* have a `MAILER-DAEMON` and `postmaster` alias present:
|
||||||
|
|
||||||
|
```
|
||||||
|
MAILER-DAEMON: postmaster
|
||||||
|
postmaster: root
|
||||||
|
```
|
||||||
|
|
||||||
|
Note how you can have referential aliases; mail to `postmaster` is aliased to `root`, which is aliased to `revsuine`,
|
||||||
|
so ultimately `revsuine` will get `postmaster`'s mail.
|
||||||
|
|
||||||
|
You can continue to populate the aliases file with whatever aliases you want.
|
||||||
|
|
||||||
|
<!-- FOOTNOTES: -->
|
||||||
|
|
||||||
|
[^postfix_aliases_location]: Your aliases file will most likely be in this location by default, but you can run
|
||||||
|
|
||||||
|
$ postconf alias_maps
|
||||||
|
|
||||||
|
to find out where this file should be.
|
||||||
|
|
||||||
|
|
@ -6,12 +6,12 @@ title = 'Contact'
|
||||||
Toc = false
|
Toc = false
|
||||||
+++
|
+++
|
||||||
|
|
||||||
## Email
|
# Email
|
||||||
|
|
||||||
You can email me at `pid1 at revsuine dot xyz`. Please use [my GPG key](/revsuine_public_key.asc) (fingerprint
|
You can email me at `pid1 [at] revsuine [dot] xyz`. Please use [my GPG key](/revsuine_public_key.asc) (fingerprint
|
||||||
`8FB4 18CD 9520 22E5 BBC4 3261 3F25 7B68 F5BC 9339`) to encrypt emails to me.
|
`8FB4 18CD 9520 22E5 BBC4 3261 3F25 7B68 F5BC 9339`) to encrypt emails to me.
|
||||||
|
|
||||||
## Matrix
|
# Matrix
|
||||||
|
|
||||||
I can be contacted on Matrix at
|
I can be contacted on Matrix at
|
||||||
|
|
||||||
|
|
|
||||||
|
|
@ -12,6 +12,9 @@ theme = 'terminal'
|
||||||
# allow you to set tags with tags = [ 'tags', 'here' ] in post front matter
|
# allow you to set tags with tags = [ 'tags', 'here' ] in post front matter
|
||||||
tag = 'tags'
|
tag = 'tags'
|
||||||
|
|
||||||
|
[pagination]
|
||||||
|
pagerSize = 5
|
||||||
|
|
||||||
### TERMINAL THEME CONFIG ###
|
### TERMINAL THEME CONFIG ###
|
||||||
|
|
||||||
[params]
|
[params]
|
||||||
|
|
|
||||||
Loading…
Reference in a new issue