We’ve heard from quite a few of our email customers who get their internet connectivity from Verizon that they’ve started having problems sending (not receiving) email.
What’s happening: as an anti-spam measure, Verizon has started to block the SMTP port (port 25) for residential customers. There’s a Verizon writeup on this here. This is a good thing for the net because it blocks outgoing mail from virus-infected PCs (Wikipedia article here).
The workaround is simple: go into your email software setup and change the outgoing server setting from port 25 to port 587. Port 587 works with all of our servers and will let you send mail even if Verizon (or Comcast, Cox, Roadrunner etc.) blocks port 25.