No Access via IMAP

[robert.nickel]

Hi,
I'm having problems connecting to my Mail-Account, using IMAP. The funny thing is, that it works with one of my domains but not with the other.
While I do receive Mails and they get forwarded as well, I cannot connect via IMAP.
Yet I am pretty sure I have used the correct settings in my IMAP-Client for they resemble those of the other accounts which are working quite fine.

Right now I don't even know where to look for a solution! Any suggestions?

Thanks so much!

Robert