We want to know when using office 365 what authentication we should use?

The mechanism should be PLAIN

Office 365 SMTP Settings

 

• • • Server Address: smtp.office365.com
    • Username: Your Office 365 Address (e.g. [e-mail])
    • Password: Your Office 365 Password
    • Port Number: 587 (With TLS)
    • Authentication: Required
    • Sending Limits: 10,000 Emails a day
•