SMIME decrypt failed when e-mail is signed and send from Microsoft Outlook

Infos:

  • Used Zammad version: 4.1.0
  • Installation method (source, package, …): package
  • Operating system: CentOS 7
  • Database + version: PostgreSQL 9.2.24
  • Elasticsearch version: 7.14
  • Browser + version: doesn’t matter

Expected behavior:

Actual behavior:

  • If a customer send an e-mail encryted and signed from Microsoft Outlook (2013, 2016) to zammad, the e-mail can’t be decrypted although the private key is stored

  • If a customer send an e-mail encryted and not signed to zammad, the e-mail will be decrypted

  • We have the problem with our users here on site and with our customers

  • The strange thing is, emails decrypted and signed from Mozilla Thunderbird are decrypted in zammad without any issues

I learnd, that my problem is no bug, but a technical question (SMIME decrypt failed when e-mail is signed and send from Microsoft Outlook · Issue #3734 · zammad/zammad · GitHub) - so, can anyone give me a hint how to resolve my problem?