As of July 2010, the situation was like this. (In our area, Verizon's wired accounts are being taken over by Frontier Communications as of 2010-07-28, so I won't be able to personally verify any changes to Verizon's technical configuration. --Woozle 21:28, 28 July 2010 (UTC))
- Verizon does not block port 110, necessary for retrieving email from a remote POP3 server or for hosting one's own POP3 server. (...though I think they did at one point.)
- Verizon does not block ports 143 or 993, necessary for retrieving email from a remote IMAP server or for hosting one's own IMAP server.
- Verizon blocks port 25, which is necessary for SMTP (outgoing email).
- This means that if Verizon is your ISP, you have to use Verizon's SMTP servers to send email.
- Verizon's servers block outgoing email whose return address is not a domain owned or hosted by them...
- ...unless the sender authenticates using an existing Verizon user/password.
As of 2010-07-28, as customer accounts were being "transferred" over to Frontier's servers, Verizon's SMTP server (incoming.verizon.net) stopped recognizing my consulting client's login credentials, while Frontier's SMTP server (smtp.frontier.com) was not yet responding to hails. My client was therefore unable to send email from their office network, and had to resort to using their mobile devices (2 Blackberrys and an iPhone) or calling customers on the phone. --Woozle 21:28, 28 July 2010 (UTC)