doesn't find new messages

[Erwin Kaiser]

I'm new to mutt and first of all want to thank all developers: I like it
very much!
What I don't understand is that the manual promises that <tab> goes to the
next unread message in the mailboxes specified by the mailbox command.
I listed all I feed by procmail but I have to change manually - via "c" - to
the folders where the new unread messages are stored. 
Thanks for any hints!
Erwin