Hopefully this helps you.
I suddenly stopped receiving my verizon.net emails in my Outlook. I worked with Verizon tech support people for 17 days and finally a microsoft support tech helped to get my problem ....
VERIZON had BLACKLISTED my router's public IP address. Had to get to their Tier 2 support and have them WHITLIST my router's public IP address.
To find your router's public IP address, open internet explorer nad type into the address line "Whats my IP address?" It comes right up. Then...
Go to www.verizon.net/whitelist to submit request to be whitlisted, OR
email their security team at email@example.com .
Good luck. It took me 17 days of working with live tech support people from Verizon (my webmail), AT&T (my internet provider here at this home) and my wonderful Microsoft Outlook support person: Rose. Rose even had conference call with the Verizon technicians for hours at a time and where both Rose (MS tech) and Verizon were remoted into my PC. Verizon kept denying it was their problem but Rose showed them the error of their ways.
Thank you, Rose at Microsoft!