Outlook login fail to IMAP server

@SteveM8, have you already gone to the Xfinity Email website.
Check the Access Security box to turn on access to third-party email programs.

Otherwise, you may get an error message when attempting the steps below. Follow these instructions to turn on access.

Configure Microsoft Outlook 365
Open Outlook.
Click the File menu.
Click Add Account
Enter your Xfinity Email address (e.g., yourname@comcast.net)
Enter your Xfinity Email password, then click Connect
Click Done when your account was successfully added

If you need to update information, 
Click File.
Click Account Settings, then Account Settings from the drop-down menu
Select your email account, then click Repair
Click Advanced Options.
Place a checkmark next to Let me repair my account manually.
Click Repair.
Enter your new password
Click Next.
Congratulations! You're done reconfiguring your Outlook client to send and receive Xfinity Email.