m-law in this case that will not work as Microsoft deprecated basic auth a long time ago.
vaishnaviagarkar I will say I haven’t seen this error before. Go to the database, go to the _email table, copy the ID for the email in question, go to the _email_account table, find the records where email_id equals the ID you copied, and delete those records. Then navigate back to the email in osTicket and retry.