Does Exchange Online SMTP Relay Use Basic Authentication?
Question details
Organizations need to know whether SMTP relay configurations from printers or applications via Microsoft 365 MX endpoints on port 25 are affected by the deprecation of Basic Authentication.
- Product
- Microsoft Exchange Online
- Device & OS
- not provided
- Scenario
- Administrators are configuring or auditing SMTP relay setups for network printers and legacy applications using Microsoft 365 to send emails.
- Observed behavior
- Clarification is required regarding authentication dependencies for port 25 MX endpoint SMTP relay following Microsoft's retirement of Basic Authentication.
Verify your current application or network printer settings to determine exactly which port (e.g., 25 or 587) and SMTP endpoint your devices are utilizing.
Evaluate MX Endpoint and Port 25 SMTP Relay Configurations
Determine if your specific setup relies on Basic Authentication by distinguishing between standard SMTP relay and authenticated SMTP submission.
Microsoft's retirement of Basic Authentication primarily impacts protocols that pass traditional username and password combinations, such as POP, IMAP, and Authenticated SMTP (SMTP AUTH, typically on port 587).
If you are using a Microsoft 365 MX endpoint on port 25 with an accepted domain (often called Direct Send or Microsoft 365 SMTP relay), this setup typically uses IP address or certificate-based routing rather than standard Basic Authentication, meaning it operates separately from the deprecated methods.
Log into your printer or application's admin panel and navigate to the network or email configuration section. Confirm whether the outgoing server port is set to 25.
Ensure the SMTP server is configured to your MX endpoint (e.g., yourdomain-com.mail.protection.outlook.com) rather than smtp.office365.com.
Check the security settings in the same menu to ensure TLS encryption is enabled, which is recommended for securing port 25 transmissions.
Consult the Exchange Online IT Professionals Forum
Because tenant security policies can vary, seeking expert confirmation on your unique SMTP routing setup ensures compliance with Microsoft's current standards.
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Frequently Asked Questions
What is the difference between SMTP Relay and SMTP Client Submission in Microsoft 365?
SMTP Client Submission (usually port 587 via smtp.office365.com) requires a licensed Microsoft 365 mailbox and uses username/password authentication. Microsoft 365 SMTP Relay (often port 25 via an MX endpoint) authenticates using your public IP address or a TLS certificate, which is typically used for sending emails to external recipients from internal devices.
Does the retirement of Basic Authentication disable all SMTP services?
No. While Microsoft disabled Basic Authentication for Exchange Online protocols by default to enhance security, SMTP AUTH (Basic Auth for SMTP) can still be temporarily re-enabled at the tenant or mailbox level if absolutely necessary. However, transitioning to Modern Authentication (OAuth) or alternative relay methods is strongly recommended.
Can my office printer still send emails if it doesn't support Modern Authentication?
Yes. If your multifunction printer does not support OAuth, you can bypass the need for Basic Authentication by configuring the device to use Direct Send or Microsoft 365 SMTP relay over port 25, provided you have a static public IP address or accepted domain configuration.
