dovecot: enable lz4 compression on disk

CHANGELOG.md

@@ -21,6 +21,9 @@
 - filtermail: do not allow ASCII armor without actual payload
   ([#325](https://github.com/deltachat/chatmail/pull/325))
 
+- dovecot: enable lz4 compression on disk
+  ([#341](https://github.com/deltachat/chatmail/pull/341))
+
 ## 1.3.0 - 2024-06-06
 
 - don't check necessary DNS records on cmdeploy init anymore

cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2

@@ -38,7 +38,14 @@ service imap {
 mail_server_admin = mailto:root@{{ config.mail_domain }}
 mail_server_comment = Chatmail server
 
-mail_plugins = quota
+# `zlib` enables compressing messages stored in the maildir.
+# See
+# <https://doc.dovecot.org/configuration_manual/zlib_plugin/>
+# for documentation.
+#
+# quota plugin documentation:
+# <https://doc.dovecot.org/configuration_manual/quota_plugin/>
+mail_plugins = zlib quota
 
 # these are the capabilities Delta Chat cares about actually 
 # so let's keep the network overhead per login small
@@ -96,17 +103,14 @@ mail_privileged_group = vmail
 # Pass all IMAP METADATA requests to the server implementing Dovecot's dict protocol.
 mail_attribute_dict = proxy:/run/chatmail-metadata/metadata.socket:metadata
 
-# Enable IMAP COMPRESS (RFC 4978).
+# `imap_zlib` enables IMAP COMPRESS (RFC 4978).
 # <https://datatracker.ietf.org/doc/html/rfc4978.html>
 protocol imap {
-  mail_plugins = $mail_plugins imap_zlib imap_quota
+  mail_plugins = $mail_plugins zlib imap_zlib imap_quota
   imap_metadata = yes
 }
 
 protocol lmtp {
-  # quota plugin documentation:
-  # <https://doc.dovecot.org/configuration_manual/quota_plugin/>
-  #
   # notify plugin is a dependency of push_notification plugin:
   # <https://doc.dovecot.org/settings/plugin/notify-plugin/>
   #
@@ -118,7 +122,11 @@ protocol lmtp {
   #
   # Sieve to mark messages that should not be notified as \Seen
   # <https://doc.dovecot.org/configuration_manual/sieve/configuration/>
-  mail_plugins = $mail_plugins quota mail_lua notify push_notification push_notification_lua sieve
+  mail_plugins = $mail_plugins mail_lua notify push_notification push_notification_lua sieve
+}
+
+plugin {
+  zlib_save = lz4
 }
 
 plugin {