Yesterday I was thinking about the process of copying mailbox data from an old Pegasus Mail installation to a new one. When I have done it in the past, I have copied the .PND files (POP3 and SMTP host configuration files) to the new installation without a thought to including the POP3 associated .PM3 file (the file that keeps a record of retrieved messages). In theory, without the .PM3 file the first POP3 retrieval by the new installation should have brought down all messages on the server. I don't recall that ever happening though. Only the messages received since the last POP by the old installation were retrieved. Can any explain this and how the .PM3 file fits into the process?

Looks like Pegasus Mail never ever touched it again after February 2011 and it's definitely not read-only ...

PS: ... and I'm using almost exclusively POP3 with this account.

That's strange. At first glance it appears that mine are date/time stamped as of the last retrieval of a message on the associated account. I have four active POP3 accounts in one of my PMail instances and three in the other along with a bunch of unused .PND files so I plan to do more analysis once I match .PM3 to .PND. I don't think that will shed any insight into how they work though. It will only confirm whether they are updated at every message retrieval.

My analysis of .PM3 file updating has revealed that they get modified each time the associated account is checked for messages provided there are messages in the inbox on the server.

Additionally, the removal of a .PM3 file resulted in a re-download of the messages in that servers inbox. I don't remember any trauma associated the mass download of existing messages when I have done a clean installation and either created new POP3 host files to existing accounts or copied the .PND files from a previous installation. It is possible that I had the foresight to use web interfaces to empty the server inboxes first. I sure wish I could remember.