Comcast email transition to Yahoo

See whether below can help:

1. Use Outlook Classic
•    Since it works reliably with Yahoo’s app password, stick with it until Microsoft and Yahoo resolve the sync issue.
•    You can disable the “Try the new Outlook” toggle to stay in Classic mode.
2. Try Adding the Account via IMAP in New Outlook (Advanced Setup)
•    Go to New Outlook > Add Account > Advanced Setup > IMAP
•    Use these settings: 
o    Incoming server: imap.mail.yahoo.com, Port: 993, SSL: Yes
o    Outgoing server: smtp.mail.yahoo.com, Port: 465 or 587, SSL: Yes
o    Username: your full Comcast.net email
o    Password: Yahoo app password (not your regular password)
3. Generate a Fresh App Password in Yahoo
•    Go to your Yahoo account security settings
•    Generate a new app password specifically for Outlook
•    Use this new password when setting up the account
4. Avoid OAuth Setup for Now
•    The new Outlook tries to use OAuth for Yahoo, which may not be fully supported for Comcast.net aliases.
•    Stick to manual IMAP setup with app password until OAuth integration is stabilized.