Sign in to Redant as Admin
From the Main Menu select Maintenance>Users>Login ID
Locate the User to change or select New to create a new user and then add the following settings:
SMTP Port: 587
SMTP Server: smtp.office365.com
SMTP User Name: your full email address e.g. fred@abc.co.uk
SMTP Password: your 365 password
TLS / SSL: Both Options Checked
Authentication: 1
Once the new settings have been saved then select 'Test Email' button to verify