Does smtp.office365.com Require TLS for SMTP AUTH?
Question details
The user needs to know if plain-text communication is allowed or if TLS is strictly required when configuring a printer or scanner to send emails via Microsoft 365 using smtp.office365.com on port 587.
- Product
- Microsoft 365 Exchange
- Device & OS
- Epson printer or scanner
- Scenario
- Configuring a networked device to send scanned documents via email through Microsoft 365 using SMTP AUTH.
- Observed behavior
- The user is determining the required encryption protocol (TLS vs plain-text) for establishing a successful SMTP connection to prevent Microsoft 365 from rejecting the request.
Ensure you have the administrative login credentials for your printer's web interface and the Microsoft 365 email account details that will be used to send the emails.
Enable TLS 1.2 for SMTP AUTH on Your Device
Configure your printer or scanner to use TLS 1.2 with STARTTLS on port 587 to securely connect to the Microsoft 365 SMTP endpoint.
Microsoft 365 strictly requires TLS for client connections to the smtp.office365.com endpoint. Plain-text SMTP communication is permanently disabled for security reasons. If your device attempts a plain-text connection, Microsoft 365 will actively reject the SMTP AUTH request.
Open a web browser on a computer connected to the same network as your printer or scanner and enter the device's IP address to access its administrative web interface.
Locate the Network, Network Settings, or Email/Scan-to-Email configuration menu within the device's web interface.
In the SMTP Server or Hostname field, type 'smtp.office365.com'.
Set the SMTP Port to 587. Enable 'STARTTLS' or select 'TLS 1.2' from the encryption dropdown menu, ensuring plain-text communication is disabled.
Enter your Microsoft 365 email address and password in the SMTP Authentication fields, save the settings, and run a connection test from the device.
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Frequently Asked Questions
What port should I use for smtp.office365.com?
You should use port 587 when connecting to smtp.office365.com using SMTP AUTH with STARTTLS. Port 25 is typically used for SMTP relay rather than direct client authentication.
Why is Microsoft 365 rejecting my SMTP AUTH request?
Microsoft 365 rejects SMTP AUTH requests if the connecting device attempts to use plain-text communication, uses an unsupported legacy TLS version (like TLS 1.0 or 1.1), or if the SMTP AUTH protocol is disabled for your specific tenant or user mailbox.
Can I use SSL instead of TLS for Microsoft 365 SMTP?
Microsoft 365 requires TLS (specifically TLS 1.2 or higher) via the STARTTLS command. Legacy SSL connections are generally deprecated and unsupported for secure Exchange Online email submission.
What if my printer does not support TLS 1.2?
If your legacy scanner or printer lacks TLS 1.2 support, you cannot connect it directly to Microsoft 365. You can work around this by configuring a local SMTP relay using Windows IIS or a third-party application to accept local traffic and forward it securely to Microsoft 365.
