jjoerg:

That's because you're expecting a bit too much from MIME::Parser--it wants a thing with MIME in it, and you're passing it an entire mailbox. Try using a module to parse the mailbox into individual messages (such as Mail::Box or similar). Then you can examine the EMail to see if you've processed it or not. For the ones you haven't, call the MIME::Parser to do your extractions.

...roboticus

When your only tool is a hammer, all problems look like your thumb.