On our company we were using a local human resources app, which I had configured to SMTP relay to M365 just fine, following the steps here: https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-microsoft-365-or-office-365#option-1-authenticate-your-device-or-application-directly-with-a-microsoft-365-or-office-365-mailbox-and-send-mail-using-smtp-auth-client-submission
But today the local app was discontinued by the provider, and migrated to a web service. Thing is, if I replicate the MAPI config currently on the local app (config options are the same), I can't get it to work.
Tried to modify the connector so it would accept mail from the web domain instead of the local IP, to no avail. Also created a new 3rd party connector, with the same outcome. So I guess am barking at the wrong tree.
Appreciate any help on the subject. Thanks!