The Washington Post is reporting that Verizon will now use port 587 for mail submission.

Verizon network has often been reported by spamhaus to be a major source of spam and recently was listed to be the number 19 network worldwide source of spam. Compromised machines (zombies) on Verizon network are sending spam via its mail servers or directly to the Internet. Verizon has decided, it seems, to block port 25 (smtp) and to require its customers on dynamic IPs to use port 587 (submission) to send emails via its mail servers.

The main difference from port 25 is that port 587 requires authentication, as specified in the draft standard RFC 4409.

Verizon will still continue to use port 25 to receive emails for its domains, but for relaying emails from its customers on dynamic IPs, Verizon customers will have to use this more secure protocol. As an individual user it does not require new software but to configure your mail client to use this port instead of port 25 and to enable authentication when submitting emails.

It is good news that Verizon has decided to handle their spam problem and I hope other networks will follow suit to reduce the amount of spam generated by botnets and zombies.