WebHelp Desk Java issues

We have upgraded to the latest 12.5.

Since doing this incoming email is no longer working.

A quick check of the settings makes it appear to be OK, but thgen pressing OK at the bottom then makes the system complain the username for authentication requires the domain\username configuration.

When I change it and click OK, it fails with an error:

We're sorry, an unexpected error occurred:

java.lang.OutOfMemoryError: Java heap space

Any thoughts would be gratefully received, as we are not currently able to submit tickets via email!