Microsoft has announced the end of Basic Authentication for sending email via Microsoft 365 in early 2026. Applications and devices will no longer be able to use Basic Authentication when using Client Submission (SMTP AUTH) to send email via Exchange Online.

Previously Microsoft removed the ability to receive email using Basic Authentication in late 2022. Removal of the ability to send email using Basic Authentication was scheduled for September 2025, but was delayed to give more time for this transition.

This is part of Microsoft’s ongoing efforts to strengthen account security and reduce the risk of phishing, brute-force attacks etc. But this also forms part of Microsoft’s more subtle move to ensure Microsoft 365 email be used for comms only, and not for other applications such as multifunction devices and programmatic messages. Restricting these other uses will help manage abuse on their platform, but will also reduce the volume of email overall thereby likely reducing their operating costs – e.g. if all organisations can no longer use Microsoft 365 email for scan-to-email or notifications functionalities.

Key dates

• 1 March 2026 31 December 2026
  Basic Authentication will be disabled for existing customers, although it can be re-enabled if needed. Basic Authentication will be unavailable for new customers, with no recourse.
• 30 April 2026 H2 2027
  Microsoft will announce the final depracation date for Basic Authentication.

If you’re still using Basic Auth to send emails — for example, from websites, applications, scanners, multifunction printers — you’ll need to update your configuration. After the cut-off date, all these systems will no longer be able to send email via Exchange Online (Microsoft 365) until they use a supported authentication method.

You will need to switch to OAuth to continue using Microsoft 365 to send emails in this way, if your systems support modern authentication methods. Otherwise, you may need to switch to another solution that allows for sending programmatic and high message volumes.

Microsoft is offering a new pay-as-you-go high volume email sending service via their Azure Communication Services. And we offer a fixed rate high volume email sending service: please see our SMTP Email here.

Update 12 February 2026

Microsoft has announced a change to this deprecation timeline, and we have updated the dates above accordingly. The overall process and intention remains, but Microsoft has said that more time is being given following customer feedback and to provide additional runway for adoption progress.