/usr/share/otrs/Kernel/System/PostMaster/ is in otrs2 6.0.5-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/otrs/Kernel/System/PostMaster/DestQueue.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/
/usr/share/otrs/Kernel/System/PostMaster/Filter.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/CMD.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/Decrypt.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/DetectAttachment.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/DetectBounceEmail.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/ExternalTicketNumberRecognition.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/FollowUpArticleVisibilityCheck.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/Match.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/MatchDBSource.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/NewTicketReject.pm
/usr/share/otrs/Kernel/System/PostMaster/Filter/SMIMEFetchFromCustomer.pm
/usr/share/otrs/Kernel/System/PostMaster/FollowUp.pm
/usr/share/otrs/Kernel/System/PostMaster/FollowUpCheck/
/usr/share/otrs/Kernel/System/PostMaster/FollowUpCheck/Attachments.pm
/usr/share/otrs/Kernel/System/PostMaster/FollowUpCheck/Body.pm
/usr/share/otrs/Kernel/System/PostMaster/FollowUpCheck/BounceEmail.pm
/usr/share/otrs/Kernel/System/PostMaster/FollowUpCheck/RawEmail.pm
/usr/share/otrs/Kernel/System/PostMaster/FollowUpCheck/References.pm
/usr/share/otrs/Kernel/System/PostMaster/FollowUpCheck/Subject.pm
/usr/share/otrs/Kernel/System/PostMaster/LoopProtection/
/usr/share/otrs/Kernel/System/PostMaster/LoopProtection.pm
/usr/share/otrs/Kernel/System/PostMaster/LoopProtection/DB.pm
/usr/share/otrs/Kernel/System/PostMaster/LoopProtection/FS.pm
/usr/share/otrs/Kernel/System/PostMaster/LoopProtectionCommon.pm
/usr/share/otrs/Kernel/System/PostMaster/NewTicket.pm
/usr/share/otrs/Kernel/System/PostMaster/Reject.pm