Bugzilla

Hi Bron, Thanks for the info.
Testing with two TB clients to same fastmail account/server, when I mark \deleted a message on client A, all I see on client B imap log is the same message UID  with \deleted flag set. I don't see an EXPUNGE reported on client B for that message until I shutdown client A. (The EXPUNGE is reported in an IDLE response.) So there doesn't seem to occurring an "insta-expunge" when \deleted flag is set like gmail does.
Since both TB clients are configured to "just mark deleted messages as \deleted", on shutdown TB sends just LOGOUT (not CLOSE) so per https://datatracker.ietf.org/doc/html/rfc3501#section-6.4.2 an expunge should not occur.
Maybe I'm not understanding your answer since I'm not really familiar with what JMAP has to do with this. 
Also, FWIW, the distro supplied cyrus version I run (just for testing TB issues) doesn't have this issue (messages marked \deleted are not expunged after LOGOUT).

Hi Bron, Thanks for the info.
Testing with two TB clients to same fastmail account/server, when I mark \deleted a message on client A, all I see on client B imap log is the same message UID  with \deleted flag set. I don't see an EXPUNGE reported on client B for that message until I shutdown client A. (The EXPUNGE is reported in an IDLE response.) So there doesn't seem to be an "insta-expunge" occurring when \deleted flag is set like gmail does.
Since both TB clients are configured to "just mark deleted messages as \deleted", on shutdown TB sends just LOGOUT (not CLOSE) so per https://datatracker.ietf.org/doc/html/rfc3501#section-6.4.2 an expunge should not occur.
Maybe I'm not understanding your answer since I'm not really familiar with what JMAP has to do with this. 
Also, FWIW, the distro supplied cyrus version I run (just for testing TB issues) doesn't have this issue (messages marked \deleted are not expunged after LOGOUT) and there is no auto/insta-expunge when a message is marked \deleted.