I have corrected several typos in my response below. Then I must go do
some real work until my brain starts working properly again!

(I am assuming you are downloading from multiple servers
simultaneously, and not trying to download a bunch of messages from a
single account; I don't believe POP3 even supports the latter)

First, be careful *not* to share resources without synchronization:
two threads shouldn't write to the same file simultaneously, for
example. Mutexes, critical sections and semaphores can be useful for
this, depending on the circumstances.

I would look around on SourceForge, CodeProject, and CodeGuru for
projects that do similar things -- perhaps as servers -- and learn
about synchronization between threads.

Since your application is a client, it can start a thread for each
POP3 server. If the e-mails are being written to separate files, you
only need to coordinate file names between the threads; if appended to
a single mailbox *file*, then the threads will have to wait for each
other to finish writing a message before beginning to write their own.

Another option would be for each receiver thread to write each message
to a temp file. An additional thread would be signaled when a file is
complete and append it to the inbox.

I hope this helps and gives you some ideas.

--
Sev

I assumed he meant different POP3 servers or at least accounts (I use
3 servers and 5 accounts). I don't think the POP3 protocol even allows
multiple connections to the same account.

--
Sev