Thank you for the fast answer and the very helpful link.
Refering to that page, the PNX files are queued messages. I deleted all messages "ready to send" but there were two without any content, i can't delete. ( They just reappeared after i restartet PMail)
I moved these files (the 2gb and another 500mb file with their sorresponding ones) to antoher folder an the odd queued messages were gone. I guess there must have been some internal fault of Pegasus with these two messages.
As long as all my mails are still in their folders they belong in I am happy! :-)
Thanks a lot!
kind regards