Enable Mail Fetching on Test Environment

Enable Mail Fetching on Test Environment

We have a test environment set up for ServiceDesk. This is so we can do the obvious testing of anything new in the updates or any big scripts/functions we'd like to use on our production version.

I've created an account in AD and assigned it a 365 G1 license so it can send and receive email. I've then added it to the Incoming and Outgoing Mail Server Settings. However when I enable Mail Fetching I get the below message.

"Mailbox is not accessible : "Unable to connect to mail server. Check configurations and try again.". In the meantime, mails will not be fetched in the mail fetching schedule."

What may be the cause of this? Are we only able to have one live version of SDP?