Verizon Mail Bounces Back?

I can't sent e-mail successfully to ANY Verizon.net address. After a few days, it bounces back from MAILER-DAEMON@n5.bullet.mail.ac4.yahoo.c… with a message that Mail server for verizon.net unreachable for too long. I can send fine from my AOL account. I want Yahoo as my primary account but this is a problem.