Max. message size (attachment size)

Open data/conf/postfix/ and set the message_size_limit accordingly in bytes. See for the default value.

You will also need to adjust message size in Rspamd and Clamav configurations:

  • in data/conf/rspamd/local.d/ add max_message parameter, check Rspamd Docs for defaults
  • in data/conf/rspamd/local.d/external_services.conf adjust max_size parameter for oletools
  • in data/conf/rspamd/local.d/antivirus.conf adjust max_size parameter for clamav
  • in data/conf/clamav/clamd.conf adjust MaxScanSize and MaxFileSize

Restart Postfix, Rspamd and Clamav:

docker compose restart postfix-mailcow rspamd-mailcow clamd-mailcow
docker-compose restart postfix-mailcow rspamd-mailcow clamd-mailcow