BT Connect email not syncing with Mac Mail

Following the recent update of iOS to Ventura 13.3.1, my btconnect.com email address is no longer syncing with Mac Mail. The same issue is also happening on my iPhone after a similar update to the iOS.

Not setting on the email account have changed, but Mail is now unable to verify the account and doesn't recognise by btconnect email password.

The issue isn't with btconnect, as I am about to sign in via a web-browser it's just with Mail that there is an issue. Any suggestions?

Thanks,

S