If so, maybe the user you’ve configured doesn’t have SMTP Auth enabled in Exchange Online? Maybe you can also try modern authentication, or anonymous?
If that doesn’t help, I would suggest that you contact support, which is possible during trial/evaluation. Especially because of your second issue with Slack.
If so, maybe the user you’ve configured doesn’t have SMTP Auth enabled in Exchange Online? Maybe you can also try modern authentication, or anonymous?
If that doesn’t help, I would suggest that you contact support, which is possible during trial/evaluation. Especially because of your second issue with Slack.