The SMTP session fails as follows. I've redacted the b.1 test address below but it is one we have used successfully for a while.
STARTTLS succeeds
SASL authentication succeeds - we are using the credentials list in the More Info window.
235 Authentication Successful
MAIL FROM:<{address redacted}>
250 2.1.0 Sender <{address redacted}> OK
503 5.7.1 Incorrect Authentication for Specified Email Address
The 503 error is new since Monday. We are using the SASL authentication specified for this test so this error suggest a misconfiguration of the validation logic in the james server.
The SMTP session is aborted at this point since the recipient cannot be specified.