[IMAP] Das Erstellen oder Ändern des Ordners ‘/Posteingang/Spam’ ist fehlgeschlagen mit folgendem Fehler: Mailbox name not allowed (0.004 + 0.000 + 0.003 secs).
[IMAP] Creating or modifying the folder ‘/Inbox/Spam’ failed with the following error: Mailbox name not allowed (0.004 + 0.000 + 0.003 secs
That usually means you are trying to create a Spam or Junkmail folder either directly under your email account or under your account Inbox that already has a server created one so is denied.