Using a recent version of dovecot (2.3.7.2) fixed this issue. Thanks to all!
Holger 19. August 2019 16:12, "Holger Dehnhardt via dovecot" <dovecot@dovecot.org> schrieb: > Wow, that's great! Why didn't I found it... > Sorry and thanks! > > Holger > > 19. August 2019 16:08, "Alexander Dalloz via dovecot" <dovecot@dovecot.org> > schrieb: > >> Am 2019-08-19 16:01, schrieb Holger Dehnhardt via dovecot: >> >>> Alexander and Aki, >>> thanks for your quick answers. >>> It might be the best to compile a more recent version of dovecot. For >>> some reason it seems unpossible to get a core dump and the error might >>> be fixed in a recent version. >>> Holger >> >> https://repo.dovecot.org >> >> Alexander