Recently (since the upgrade from 4.8 beta1 to beta2?), deleting an e-mail in my (dimap) inbox only removes this e-mail temporarily. After the next sync with the server, all deleted mails are back. Re-starting Akonadi did not help, neither did logging out completely and logging back in. Not sure what other information might be useful, please ping me on irc (dilfridge on #kontact or #kde-devel) if you have specific questions.
do you use a trash on your dimap account ?
No, trash was always local. I "solved" the problem... for some reason, kmail had forgotten which folder to use as trash. Re-setting the local trash as trash folder of my dimap account makes the deleting work again. (I found this because none of the "not-really-deleted" messages ended up in the trash folder!) Not sure if or where there is a bug, resolve as you see fit.
Confirmed. I encounter the same problem with kmail 4.8.1 (openSUSE-12.2 milestone-2 (march-2012)). - When I change the trash to a local trash folder, emails are removed. - When I set the trash to my other IMAP server (cyrus imap), the emails are also removed. However, the emails are not removed when a the dovecot (2.1.x) IMAP server is used. - In case of cyrus, I see IMAP messages passing by when I delete the email (this server is located on another box than the client) - I don't see any IMAP messages when I delete email from my INBOX on dovecot (perhaps the latter is the case because the dovecot IMAP server is on the same system as my IMAP client)?
With kmail 1.13.7 (or KDE-4.6.5) removing emails from the (same) dovecot server is working.
Has been working fine for quite some time now (I'm on 4.9.98 now). Most likely fixed.