Issue:  
When sending an e-mail from fusion an error message is logged: 

SmtpCmdResp: 535 5.7.3 Authentication unsuccessful [YQBPR0101CA0094.CANPRD01.PROD.OUTLOOK.COM] SMTP authentication failed after sending password.  Check your username/password or your SMTP server's auth settings

Reason(s):
- Azure Portal Policy Enable Security Defaults are set to Yes witch disable the SMTP Authentication

- User has SMTP Authentication unchecked

- MFA (Multi-Factor Authentication) is Enabled on the account which prevents SMTP Authentication

Solution:

Part 1 - Confirm SMTP Settings:

Office 365 SMTP server address: smtp.office365.com
Office 365 SMTP port for (TLS/STARTTLS): 587

Part 2 - Set Enable Security defaults to NO

- Log in to Azure Portal https:https://portal.azure.com/ using the Admin account email and password
- Please note that you must have access to the device that provides the Authentication Codes or has the Microsoft Authenticator mobile app installed. Code is an additional security measure and is used in conjunction with e-mail and password to login to the Azure Portal website.
- After login click - Azure Active Directory - Properties - Manage Security defaults link

- Under Enable Security defaults, click No

Part 3 - Enable SMTP Authentication Under the User

- Login to the Office 365 with Admin user account, click on  Users - Active users section https://admin.microsoft.com/AdminPortal/Home?#/users

- Select the user that will be used to login (Ex: Test User)

- Click on the Mail tab and Manage e-mail apps link

- Select Authenticated SMTP and Save the changes

Part 4 - For users with MFA Enabled set the setting to Allow users to create app passwords to sign in to non-browser 

- Login to the Office 365 with Admin user account, click on  Users - Active users section https://admin.microsoft.com/AdminPortal/Home?#/users

- Click on Multi-factor authentication link

- Click service settings

- Click Allow users to create app passwords to sign in to non-browser apps and click save

Part 5 - For the users with MFA enabled create an App password

- Login to Office 365 with the User (Ex: Username testuser@test.onmicrosoft.com) used to send e-mail and click this link  https://account.activedirectory.windowsazure.com/Proofup.aspx

- Click App Password link

- Click create

- Under the Name: type in Fusion press next

- copy the password

- Open Fusion and under Email tab and the Username and Password

(Ex: Username testuser@test.onmicrosoft.com Password: bmdxj........) click OK