Code:
Caused by: java.io.EOFException: SSL peer shut down incorrectly
I think that's an End of File exception.
Do you have a commercial cert? You may want to reinstall it.
Do you know if it's just one client, or many. If it's many, that may indicate some weird problem with the keystore?
If it's one, try resetting their account on their pop3 client. Is this outlook/windows?