This app password can be pasted into the PhoneBurner SMTP Password section, instead of using your actual office365 password.
This is information from the support article: "An app password is a code that gives an app or device permission to access your Office 365 account."
If your admin has set up 2-step verification for your organization, and you're using apps that connect to your Office 365 account, you'll need to generate an app password so the app can connect to Office 365.
SMTP Microsoft Outlook Setup Guide
Click on the drop down menu to the right of your user icon in the top right corner of the PhoneBurner window, click on Email Settings.
On the left of the screen you will see a list of items, please click on SMTP server
Choose your SMTP provider- click on the dropdown to select Office365 API.
Click on the Login with Office365 button
Click on the Update Settings button
If it works then you will see a the Personal SMTP server button go green.
If there is an error when trying to connect, follow these steps:
Double check with the user that they entered their Microsoft Outlook password into the SMTP Password field and that their Caps Lock is not on.
Do they have an Admin on their Microsoft Outlook / Office account? I.e. are they part of a team? If so, they may have to get the admin involved to allow less secure apps and 2-factor authentication.