Manuel Lemos - 2012-10-11 00:12:15 - In reply to message 3 from Eugene Gordeev
The unique ID of messages is an identifier of each message that is unique among all received messages, in the past or future.
All messages are referenced by message number, but if for some reason you close and and reopen the POP3 server connection, message numbers may change.
So you only need to care about message unique ids if for some reason you need to access the same message in multiple distinct connections. If that is not the case, you can just reference messages by number.