IMAP Host Unreachable Errors

  • Used Zammad version: This is Zammad version 3.2.x as listed through the webUI
  • Used Zammad installation source: Official Docker via clone of zammad-docker-composer.git
  • Operating system: RancherOS & Debian 10 on ESXi 6.7.
  • Browser + version: Chrome 79.0.3945.130

Expected behavior:

  • When creating an email account to receive emails IMAP & SMTP should connect properly and stay connected without errors. Changing Email Notifications afterward from MTA to SMTP should not break IMAP connection. Using Hydroxide (protonmail-bridge) to enable IMAP/SMTP access.

Actual behavior:

  • IMAP & SMTP Connect, but then throw errors after a few minutes. Additionally, trying to change the Sendmail from MTA to external SMTP, or making any changes to existing email addresses will immediately result in a “Host not reachable!” error in the email dialog window with no way to resolve short of restarting the containers.

Logging into the zammaddockercompose_zammad-railsserver_1 container after receiving the error and using telnet, I am able to verify that IMAP and SMTP are both still reachable:

root@95a123d0e551:/opt/zammad# telnet 143
Connected to
Escape character is '^]'.
telnet> quit
Connection closed.
root@95a123d0e551:/opt/zammad# telnet 25
Connected to
Escape character is '^]'.
220 localhost ESMTP Service Ready
telnet> quit

Can’t use Channel::Driver::Imap: #<Net::IMAP::NoResponseError: search queries with NOT or OR clauses or not yet implemented>

Also get 554 5.0.0 Error: transaction failed, blame it on the weather: unknown sender address whenever I try to change the MTA setting to the SMTP bridge. This is using the same address that is able to initially connect and send properly via email setup – Note that I actually use a FQDN, but put for privacy. Searching the error message reveals that it may be related to case-sensitivity of the address, but it’s all lower case in all instances, so unless Zammad isn’t submitting it correctly, I’m not sure of the problem.

The bigger of the two issues is that IMAP doesn’t stay working.

Steps to reproduce the behavior:

Spin up rancherOS VM1, install zammad via docker method
Spin up debian 10 VM2, install hydroxide via docker method
Setup Zammad & Hydroxide, use the credentials in Hydroxide to create an email account in Zammad.
Zammad verifies account correctly.
Wait some time, or change Zammad MTA setting to SMTP. SMTP fails with error message. At the same time, another error message will show up under IMAP and IMAP no longer works. Any attempt to add another email address to the same server or change the existing one results in a 'host not reachable! error"
Reset Email notifications to MTA
Delete the email address in Zammad.
Docker-compose down && Docker-compose up -d
Re-add the email account, account verifies correctly for a time and eventually exhibits the same problems as above.

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