SUMMARY Since I upgraded from openSUSE Leap 15.0 to 15.1 I don't get a connection to the IMAP server at my work. There is an error message: "Anmeldung fehlgeschlagen, PLAIN-Anmeldung wird von diesem Server abgelehnt." Means: "Login failed, PLAIN-Authentication denied by the server." ( It's only my translation.) STEPS TO REPRODUCE 1. Add an IMAP account with the config like before 2. doesn't get a connection 3. OBSERVED RESULT The error message appears. No connection EXPECTED RESULT Should connect like it was before the upgrade SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: 5.55.0 Qt Version: 5.9.7 ADDITIONAL INFORMATION The IMAP server doesn't provide an AUTH method in his capabilities. But PLAIN should be the standard. With rainloop (in Nextcloud) and Trojita there is no problem with the connection. I tried also with my laptop with openSUSE Tumbleweed: KDE Frameworks Version 5.64.0, Qt Version 5.13.1 No connection anyway.
Even a bit weird as this report is quite old, this may match my observation to with my Kmail: Running Kubuntu 24.04: ``` kmail/noble-updates,now 4:23.08.5-0ubuntu5.1 amd64 [installed] full featured graphical email client kmailtransport-akonadi/noble,now 23.08.5-0ubuntu3 amd64 [installed,automatic] mail transport akonadi library ``` I found something - because I have TLS mitm proxy at disposal, I discovered that there is problem in PLAIN base64 calculation when composing the AUTH PLAIN payload. It should be: `<account_name>:<password> ` Problem is not related only to IMAP, but it's the case also for SMTP. What it does (IMAP - separator is not ':'): `<account_name><account_name><password>` What it does (SMTP - separator is missing) `<account_name><password>` If I replace AUTH PLAIN payloads with correctly composed ones, all works well. Since I replaced payload inline with mitm proxy, I guarantee it's not a password issue, or some user or server error/mistake. The problem is probably in the code which composes username and password into base64 payload. It _may_ be depending on CAPABILITIES sent from server, because my other IMAP/SMTP services work well.
If time allows and also you help me and direct me to likely related code parts, I can do my own research and try to contribute with a patch.