Hi Mike,
As I understand it, you can’t send emails on a mail tool via SMTP.
In my experience, the authentication may be set differently in different mail tools. In order to troubleshoot this issue, could you provide the following information?
1. You mentioned “Our external support desk tool needs to send email via smtp”. Could you give a brief introduction how the tool works?
2. Did you get the error message from the mail tool? Could you provide us with the tool’s name?
Thanks,
Lee Li