Mails don't reach Zammad and can't be sent

Infos:

• Used Zammad version: 6.3.1-1715754184.27f4405b.jammy
• Used Zammad installation type: (source, package, docker-compose, …) package
• Operating system: Ubuntu Server 22.0.4
• Browser + version: Microsoft Edge 120.0.2210.133

Expected behavior:

• Emails reach Zammad and can also be sent or forwarded

Actual behavior:

• Emails do not reach Zammad and cannot be sent or forwarded

Steps to reproduce the behavior:

I’ve found following errors in the Log:
ERROR – : Can’t use Channel::Driver::Imap: #<RuntimeError: Failed to refresh XOAUTH2 access_token of provider ‘microsoft365’: can’t alloc thread>
ERROR – : Failed to refresh XOAUTH2 access_token of provider ‘microsoft365’: can’t alloc thread (RuntimeError)

Thank you in advance for the help!