Migration failure - Server unreachable

Migration failure - Server unreachable

Hi, I'm attempting to run an IMAP migration from my previous provider, but I'm consistently running into a "Server unreachable" error message. I set up a migration last night, but left it while waiting for my MX records to be updated. I returned tonight and attempted to add the account to be migrated, but received an error message on several occasions. I then deleted the original migration and attempted to create a new one, but without any further success. I have verified that the provided details are correct and the server is reachable by my own email clients.

Any assistance would be greatly appreciated.