Problem with inbound mails in docker compose setup

Hey,

I just setup OpenProject a few days ago and came over a problem with the inbound mail config.

I setup openProject via Portainer using the github repository link to the compose file.

The initial setup works flawless, but after adding the env-vars for the inbound mail config, it doesn't works as expected:

When inviting to a meeting, the user gets an email with the info and invite as expected
Clicking on "confirm" (in Thunderbird) sends the response as expected (validated on the mailserver)
The user immediately receives another mail with the user shown as confirmed
the status of the user in the web-UI stays on "unknown"

In the cron-container log it shows repeatably:

[cron] Checking for new emails from IMAP
rake aborted!
Errno::ECONNREFUSED: Connection refused - connect(2) for 0.0.0.0:993 (Errno::ECONNREFUSED)
/app/vendor/bundle/ruby/4.0.0/gems/net-imap-0.6.4.1/lib/net/imap.rb:3505:in 'Net::IMAP#tcp_socket'
/app/vendor/bundle/ruby/4.0.0/gems/net-imap-0.6.4.1/lib/net/imap.rb:1142:in 'Net::IMAP#initialize'
/app/vendor/bundle/ruby/4.0.0/gems/net-imap-0.6.4.1/lib/net/imap/deprecated_client_options.rb:74:in 'Net::IMAP::DeprecatedClientOptions#initialize'
/app/lib/redmine/imap.rb:59:in 'Redmine::IMAP.connect_imap'
/app/lib/redmine/imap.rb:36:in 'Redmine::IMAP.check'
/app/lib/tasks/email.rake:152:in 'block (3 levels) in <top (required)>'
/app/vendor/bundle/ruby/4.0.0/gems/rake-13.4.2/exe/rake:27:in '<top (required)>'
/usr/local/bundle/bin/bundle:25:in '<main>'
Tasks: TOP => redmine:email:receive_imap
(See full trace by running task with --trace)
[cron] Rescheduling in 600s

The ENV-vars set in the stack:

TAG=17-slim
OPENPROJECT_HTTPS=true
SECRET_KEY_BASE=MySaltySalt
OPENPROJECT_HOST__NAME=op.mydomain.tld
PORT=127.0.0.1:3002
IMAP_ENABLED=true
DATABASE_URL=postgres://postgres:TOPSECRET@db/openproject?pool=20&encoding=unicode&reconnect=true
RAILS_MIN_THREADS=4
RAILS_MAX_THREADS=16
COLLABORATIVE_SERVER_URL=ws://op.mydomain.tld:3002/hocuspocus
COLLABORATIVE_SERVER_SECRET=MySecret
POSTGRES_VERSION=17
IMAP_PORT=993
IMAP_HOST=imap.provider.tld
IMAP_USERNAME=user@mydomain.tld
IMAP_PASSWORD=MySecretIMAPPassword
IMAP_CHECK_INTERVAL=120
IMAP_SSL=true
IMAP_SSL_VERIFICATION=true

The stack runs behind an Apache reverse proxy on localhost.

I'm not sure if I've missed some flag or var, or if this is indeed a bug.

Help is really appreciated as the instance should be used for our works council soon.

Content

Problem with inbound mails in docker compose setup