When a client connects to a POP3 server and authenticates, it begins a session. The session gets a snapshot of the UIDLs of each email in the mailbox at the beginning of the session, and this doesn’t change — even if new emails arrive, or emails are deleted.
Note: This is a behavior of the POP3 protocol itself. It is not specific to the Chilkat’s POP3 implementation.
The Chilkat MailMan object will automatically connect and authenticate (and begin a new POP3 session) as needed when a POP3 method requiring a session is called. The session remains open until explicitly closed or the object is destructed. Therefore, methods such as GetMailboxCount will return the same number of emails each time it is called if the POP3 session remains open while new emails arrive. To force a refresh, call Pop3EndSession (no arguments). This will end the current session, and a new session will automatically be established with the next method call.
More Information about POP3 Sessions