Click on your name in the upper right and select Advanced Settings
Click on the edit icon for SMTP
For Microsoft 365 - your settings will follow this format
Email: (your Office365 email)
Username: (your Office365 email)
Password: (your Office365 password)
SMTP Port: 587
SSL Protocol: NO
TLS Protocol: YES
From Address: Use login user email as from address.
NOTE: Office 365 has restriction about sending email on behalf of other person and due to this reason they have to do some manual setting in their office 365 account every time new email has been added in their system. Also, need to make sure all employee email belongs to their domain only otherwise it will fail in sending.
Please see below video how to give permission to send an email for other people.