Enable SMTP AUTH for a mailbox – Office 365

If you try to set up a printer / external device with SMTP you might encounter an authentication error.

This is caused by the fact that Microsoft now disables SMTP AUTH for the tenant and the new mailboxes created on Office 365 by default.

To enable SMTP AUTH for a mailbox follow this steps:

  • Go into Users
  • Click Active Users
  • Select the user
  • Click Mail
  • Click Manage email apps
  • Enable Authenticated SMTP by flagging it
  • Save

This might take a couple of hours before it’s activated.

To check where it’s enabled use the following command:

Get-CASMailbox

If it returns False under SmtpClientAuthenticationDisable, then it’s enabled.

To enable it for the whole organization send the following PS command:

Set-TransportConfig -SmtpClientAuthenticationDisabled $true