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How to Enable or Disable Authenticated SMTP in Exchange Online
Question details
The user needs to configure Authenticated SMTP (SMTP AUTH) for specific mailboxes in Exchange Online.
- Product
- Exchange Online
- Device & OS
- not provided
- Scenario
- Attempting to enable or disable SMTP AUTH for an individual mailbox when the setting is no longer visible in the portal.
- Observed behavior
- The Authenticated SMTP setting does not appear in the Exchange Admin Center due to basic authentication deprecation, requiring a PowerShell solution.
Ensure you have Exchange Online administrator privileges and have the Exchange Online PowerShell module installed and ready to connect.
Use Exchange Online PowerShell to Manage SMTP AUTH
Since the basic authentication toggle may be hidden in the Exchange Admin Center, using Exchange Online PowerShell is the most reliable method to manage SMTP AUTH.
Microsoft has deprecated basic authentication, which is why the portal interface might not display the SMTP AUTH setting. Connecting directly via PowerShell allows you to override tenant-level settings for individual mailboxes.
Open PowerShell on your computer as an administrator and connect to your Exchange Online environment using your admin credentials.
Run the command 'Set-CASMailbox -Identity <MailboxIdentity> -SmtpClientAuthenticationDisabled $false'. Replace <MailboxIdentity> with the actual email address or identifier of the user.
To turn the feature off, run the command 'Set-CASMailbox -Identity <MailboxIdentity> -SmtpClientAuthenticationDisabled $true'.
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Frequently Asked Questions
Why is the Authenticated SMTP setting missing in the Exchange Admin Center?
Microsoft has deprecated Basic Authentication across Exchange Online. As a result, the SMTP AUTH toggle is frequently removed from the web portal, and administrators must use Exchange Online PowerShell to manage the setting.
How can I check if SMTP AUTH is currently enabled for a mailbox?
You can verify the current status by running 'Get-CASMailbox -Identity <MailboxIdentity> | Format-List SmtpClientAuthenticationDisabled' in Exchange Online PowerShell. If it returns False, SMTP AUTH is enabled.
What should I do if my application still fails to send emails after enabling SMTP AUTH?
Ensure that your tenant does not have Azure Security Defaults enabled, as this blocks basic authentication globally. Additionally, check if there are conditional access policies blocking legacy authentication protocols.
