I have expierienced this silly bug for years.
Earlier versions do this too.
If you want to push such an email back to the inbox you have to touch the right one.
The duplicate will produce an error message saying it is not synchronized.
Of your synchronize your trashfolder, for some reason some messages will be doubled.
This is a bug!
-------- Ursprüngliche Nachricht --------
Von: Bast Kl <
bas...@gmail.com>
Gesendet: 30. August 2019 08:10:42 MESZ
An: K-9 Mail Developers List <
k-9...@googlegroups.com>
Betreff: [k-9-dev] double deleted mails in trashcan in gmx imap
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Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail gesendet.