mirror of
https://github.com/docker-mailserver/docker-mailserver
synced 2026-10-21 07:10:24 +02:00
a721528e3d
* docs: add Dovecot 2.4 mailbox compression guide Document the supported global mail-compress configuration, verification steps, and troubleshooting guidance for DMS 16 and later. Co-authored-by: Eric <dev@derewonko.com> Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com> * docs: remove trailing whitespace from compression guide --------- Co-authored-by: Georg Lauterbach <44545919+georglauterbach@users.noreply.github.com> Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>
106 lines
4.0 KiB
Markdown
106 lines
4.0 KiB
Markdown
---
|
|
title: 'Tutorials | Mailbox Compression'
|
|
---
|
|
|
|
## Overview
|
|
|
|
!!! warning "This is a community contributed guide"
|
|
|
|
This content is entirely community supported. If you find errors, please open an issue and provide a PR.
|
|
|
|
Dovecot provides a plugin for _mailbox compression_. This plugin enables support to read messages stored in a compressed format and to write new messages in a compressed format.
|
|
|
|
This guide applies to DMS 16 and later, which uses Dovecot 2.4 and the [`mail-compress` plugin][dovecot::plugin::mail-compress].
|
|
|
|
!!! tip "Compression algorithm"
|
|
|
|
The plugin supports several compression algorithms. For a good balance between compression ratio and performance, this guide uses `zstd`. See the [Dovecot documentation][dovecot::plugin::mail-compress] for the other supported algorithms.
|
|
|
|
!!! info "Raising the memory limit to avoid errors"
|
|
|
|
Depending on usage, compression may exceed Dovecot's [default process memory limit][dovecot::config::default-vsz-limit] of 256 MiB. The configuration below shows how to raise that limit globally if necessary; tune it for your environment.
|
|
|
|
[dovecot::plugin::mail-compress]: https://doc.dovecot.org/2.4.1/core/plugins/mail_compress.html
|
|
[dovecot::config::default-vsz-limit]: https://doc.dovecot.org/2.4.1/core/summaries/settings.html#default_vsz_limit
|
|
|
|
## Setup
|
|
|
|
Create `docker-data/dms/config/dovecot/90-mail-compress.conf` with the following configuration:
|
|
|
|
```conf
|
|
# Enable the compression plugin globally for reading and writing:
|
|
mail_plugins {
|
|
mail_compress = yes
|
|
}
|
|
|
|
# Compress new messages with zstd when they are saved:
|
|
mail_compress_write_method = zstd
|
|
|
|
# Uncomment and tune this only if Dovecot's default limit is too low:
|
|
# default_vsz_limit = 1G
|
|
```
|
|
|
|
Alternatively, add the same configuration to `docker-data/dms/config/dovecot.cf`. DMS copies that file to Dovecot's local configuration.
|
|
|
|
Add the configuration file to the `mailserver` service in your `compose.yaml`:
|
|
|
|
```yaml
|
|
services:
|
|
mailserver:
|
|
volumes:
|
|
- ./docker-data/dms/config/dovecot/90-mail-compress.conf:/etc/dovecot/conf.d/90-mail-compress.conf:ro
|
|
```
|
|
|
|
Restart DMS so it loads the new configuration:
|
|
|
|
```console
|
|
$ docker compose up -d --force-recreate
|
|
```
|
|
|
|
### Verify your configuration
|
|
|
|
After restarting the DMS container, check that `mail_compress` is enabled for the services that read and write mail:
|
|
|
|
```console
|
|
$ docker compose exec mailserver doveconf -f protocol=lmtp mail_plugins
|
|
mail_plugins {
|
|
mail_compress = yes
|
|
...
|
|
}
|
|
|
|
$ docker compose exec mailserver doveconf -f protocol=imap mail_plugins
|
|
mail_plugins {
|
|
mail_compress = yes
|
|
...
|
|
}
|
|
|
|
$ docker compose exec mailserver doveconf -f protocol=pop3 mail_plugins
|
|
mail_plugins {
|
|
mail_compress = yes
|
|
...
|
|
}
|
|
```
|
|
|
|
To verify that new mail is actually stored compressed, send a test message to an existing account and inspect the resulting Maildir file:
|
|
|
|
```console
|
|
$ docker compose exec mailserver swaks \
|
|
--server 0.0.0.0 \
|
|
--from hello@not-relevant.test \
|
|
--to john.doe@example.com
|
|
$ file docker-data/dms/mail-data/example.com/john.doe/new/*
|
|
...: Zstandard compressed data ...
|
|
```
|
|
|
|
## Troubleshooting
|
|
|
|
### Cached message size larger than expected
|
|
|
|
> ```
|
|
> dms dovecot: indexer-worker(john.doe@example.com)<1662><PLy3NgU3z2h8BgAAPDOPJQ:vWooFAY3z2h>: Error: Mailbox INBOX: UID=3: read(/var/mail/example.com/john.doe/cur/1758395999.M371909P1818.mail.example.com,S=30343,W=30821:2,S) failed: Cached message size larger than expected (30343 > 16567, box=INBOX, UID=3) (read reason=mail stream)
|
|
>
|
|
> dms dovecot: indexer-worker(john.doe@example.com)<1662><PLy3NgU3z2h8BgAAPDOPJQ:vWooFAY3z2h>: Error: Mailbox INBOX: Deleting corrupted cache record uid=3: UID 3: Broken physical size in mailbox INBOX: read(/var/mail/example.com/john.doe/cur/1758395999.M371909P1818.mail.example.com,S=30343,W=30821:2,S) failed: Cached message size larger than expected (30343 > 16567, box=INBOX, UID=3)
|
|
> ```
|
|
|
|
This can occur when importing mailboxes from another Dovecot system that were already compressed before the `mail-compress` plugin was enabled. Ensure the plugin is loaded and restart DMS with `docker compose up -d --force-recreate`.
|