Crash when select emails with checkbox

I use K9 only on my vacation phone and i transferred the version which i had on Android 2.1 again and again to the next phone. its version 4.400.
this version runs fine on Android 4.1, but when i migrate to next phone (Xperia) with Android 6, k9 crashes always when select emails (eg. for delete). Only the screen with the email list disappears, and an crash error pops um, then i see the screen for selecting folders.
actually i like this small and fast version and dont want to go the the newest one. the new interface is too much gmail lookalike
i checked on another Android 6 phone (Honor), and here is the same behavior.

Any hints?

i just found in github:
K-9 Mail v5.003 (stable)

  • Fixed crash when selecting multiple messages on Android 5.1

so i just have to try 5.003 ?

The current K9 release is 5.8x. The last release before the redesign is 5.6, but it is no longer supported. Releases of android before 10 are basically EOL … so I would suggest that you at least update to k9 5.6, and ideally 5.8 (which requires android 6 or higher). There are links in this forum on how to get the official 5.6 release. The 5.8 release is the one currently served from the google app store.