Hi,
I started with KMail as an alternative to thunderbird and already I have the first problem:
I set up an IMAP account and I can see messages from my IMAP server. I can also send E-Mail. Everything seems okay.

But I can not delete selected mail because the corresponding button is disabled.

But this only occurs on top level of the inbox.
I am able to delete mails located in subfolders of the inbox.

The mailserver is an IMAP server.

Thank you in advance for help.

I deleted the mailbox and recreated it. Now - after selecting a mail in the inbox - the Delete Button appears active
I found this odd solution here: viewtopic.php?f=215&t=117097