Mail Fetching Just Stops

Two Days ago, I noticed that SDP was no longer picking up any of the mail sent to the exchange mailbox we have set. After some troubleshooting I get this error message when I to re-enter the POP settings -> FAILURE: E-mail settings saved successfully. But error occurred while trying to check connection with mail server - Problem connecting to mailbox.

This is the second time this happen, with the first having no real reason on why it just started to work again.

So far...

I have re-enter all settings
Verified that the account is not locked out in AD
Verified that I can account mailbox in Thunderbird
Used Telnet to verified that port 25 and 110 are not being blocked
Re-Started the manage engine Services and the SDP Server it self.

All with the same outcome.

Any help would be greatly appreciated at this point, as we are coming very close to the go live date.