Mail gets confused by emails with identical Message-Id

[pabzm]

Steps to reproduce

Send an email that you receive in two ways (e.g. two mailing lists).

Expected behavior

Mail should show both emails independently.

Actual behavior

Mail shows the emails in the same thread view, as if they were referring to each other.

If I delete one of them, the other vanishes, too. It only reappears after a page reload.

If the emails don't have an identical subject (e.g. from an added prefix from a mailing list), Mail shows one subject in the messages list, and the other in the thread view as headline (see screenshot).

Mail app version

4.2.0 rcX

Nextcloud version

31 rcX

Mailserver or service

No response

Operating system

No response

PHP engine version

None

Nextcloud memory caching

No response

Web server

None

Database

None

Additional info

No response