Abort method doesn't abort the operation immediately, but only if it doesn't finish within the time interval specified by
AbortTimeout method (which is 3000 by default - 3 seconds). Unfortunately, this information is missing from
Abort method's documentation.
If you wish to abort an operation immediately, simply call
Dispose method. The
Pop3 instance won't be usable any more after this, but that would be the case for
Abort method as well if the time specified by
AbortTimeout actually elapsed. (Reason: The POP3 protocol doesn't support aborting message retrieval.)