Outlook Encryption Type Error with Office 365

Office 365 allows you to send email via SMTP based on user authentication. This is commonly used in conjunction with POP or IMAP clients. Where POP or IMAP is used for reading messages and SMTP is used to send the messages. This might also be used by applications and multi-function devices that need to send email.

To send SMTP messages through Office 365, you use the following settings:

• Server: smtp.office365.com
• User name: UPN of mailbox
• Outgoing SMTP server port: 587
• Encryption type: TLS (STARTTLS in recent versions of Outlook)

If you select the wrong encryption type then Outlook will fail to authenticate. For example, if you select the encryption type as SSL/TLS You get the following error which indicates: "Your server does not support the connection encryption type you have specified."

It's pretty rare to run into this error because most of the time, you'll be using autodiscover to configure Outlook and use the web-based protocols. However, you might run into this if you're testing to verify that an account is working properly as part of troubleshooting an app or multi-function device.