+++
title = "SMTP servers"
weight = 50
+++

Many email Message Transfer Agent (MTA) supports LMTP delivery.
Some of them are covered here.

## Postfix

Configuring Postfix requires to add these 2 lines to `main.cf`:

```ini
virtual_mailbox_domains = your-domain.tld
virtual_transport = lmtp:[::1]:1025
```

Make sure that `your-domain.org` is not already configured in the `mydomain` variable,
or it might conflict with Postfix local delivery logic.

*Indeed, Postfix internally has its default configuration for "local" mail delivery,
that maps to the old way of managing emails. LMTP delivery is a more recent, and maps
to the "virtual" mail delivery mechanisms of Postfix. Your goal is thus to deactivate
as much as possible the "local" delivery capabilities of Postfix and only allow
the "virtual" ones.*

You can learn more about Postfix LMTP capabilities on this page: [lmtp(8)](https://www.postfix.org/lmtp.8.html).

## OpenSMTPD

Something like below might work (untested):

```bash
action "remote_mail" lmtp "/var/run/dovecot/lmtp" rcpt-to virtual <virtuals>
match from any for domain "your-domain.tld" action "remote_mail"
```

The syntax is described in their manpage [smtpd.conf(5)](https://man.openbsd.org/smtpd.conf#lmtp).

## Other servers

[Maddy](https://maddy.email/) might be configured to deliver LMTP messages to Aerogramme through its [SMTP & LMTP transparent forwarding](https://maddy.email/reference/targets/smtp/#smtp-lmtp-transparent-forwarding) feature.

[Exim](https://www.exim.org/) has some support [for LMTP](https://www.exim.org/exim-html-current/doc/html/spec_html/ch-the_lmtp_transport.html) too.

[sendmail](https://www.proofpoint.com/us/products/email-protection/open-source-email-solution) might deliver to LMTP through a dedicated binary named [smtpc](https://www.sympa.community/manual/customize/lmtp-delivery.html)

<!--
Let start by creating a folder for Postfix, for example `/opt/aerogramme-postfix`:

```bash
mkdir /tmp/aerogramme-postfix
cd /opt/aerogramme-postfix
mkdir queue
```

To run Postfix, you need some users / groups setup (do it in a container if you don't want to mess up your system):

```bash
sudo useradd postfix
sudo groupadd postdrop
```

The considered `main.cf`:

```
mynetworks=127.0.0.0/8
compatibility_level=3.6
queue_directory=/tmp/postfix-test/queue
data_directory=/tmp/postfix-test/data
maillog_file=/dev/stdout
alias_database=
alias_maps=

virtual_mailbox_domains=saint-ex.deuxfleurs.org
virtual_transport=lmtp:[::1]:1025
```

The considered `master.cf`:

```
smtp inet n - n - - smtpd
smtp unix - - n - - smtp
lmtp unix - - n - - lmtp
anvil unix - - n - 1 anvil
rewrite unix - - n - - trivial-rewrite
cleanup unix n - n - 0 cleanup
qmgr fifo n - n 300 1 qmgr
tlsmgr unix - - n 1000? 1 tlsmgr
bounce unix - - n - 0 bounce
defer unix - - n - 0 bounce
trace unix - - n - 0 bounce
error unix - - n - - error
retry unix - - n - - error
discard unix - - n - - discard
virtual unix - n n - - virtual
proxymap unix - - n - - proxymap
postlog unix-dgram n - n - 1 postlogd
```
-->