I authorized my Microsoft 365 account in Unusual Suite, but when I click 'Test connection' I get an SMTP error. What's going on?

The most likely cause is that 'Authenticated SMTP' hasn't been enabled for your account. You need to turn it on at two levels: for your individual mailbox, and potentially for your entire organisation.

Enable 'Authenticated SMTP' for your mailbox

1. Open the Microsoft 365 admin center.
2. In the left navigation panel, go to Users > Active users.
3. Select the correct user. A flyout panel will appear.
4. In the flyout, select Mail.
5. In the Email apps section, select Manage email apps.
6. Find the Authenticated SMTP setting and make sure it's checked (enabled).
7. Select Save changes when you're done.

Read more on the Microsoft documentation site.

Enable 'Authenticated SMTP' for your organisation

If you've completed the steps above and still see an SMTP error when testing the connection, 'Authenticated SMTP' may also be disabled at the organisation level. You'll need to enable it using PowerShell.

1. Open PowerShell.
2. Run the following two commands in order:

Connect-ExchangeOnline

Set-TransportConfig -SmtpClientAuthenticationDisabled $false

Read more on the Microsoft documentation site.