Verizon FIOS Blocking SMTP Port (Outgoing Email)

The Long Story…

I recently found out the hard way that the Verizon FIOS Internet Service Provider (ISP) has implemented port blocking for outgoing (SMTP) email to non-Verizon mail servers. I use a third-party POP3/SMTP mail server that comes with my web hosting account (I avoid using the free email accounts that come with ISP’s like Verizon to avoid changing my email address every time I switch Internet providers). Yesterday, I noticed that my Outlook 2007 was unable to send an email. It just sat in my outbox after repeated attempts to send-and-receive. I gave up and shut down my computer for the night assuming that a reboot would fix the problem.

This morning, I tried sending the same email with the same result. Outlook kept saying it was unable to access the outgoing SMTP mail server. I was able to download email via POP3 and I was able to access my webmail. So I tried sending email through one of my web applications which uses SMTP, and to my surprise, that worked fine.

I was starting to write an email to my web host complaining that they must have changed their SMTP authentication to block external IP addresses from sending email. Then it hit me – maybe my web host isn’t the one blocking traffic. The problem could be with Verizon. So I searched around a bit and found an announcement from Verizon that explained the whole thing. I changed my Outlook settings and now I’m back in business. I’m glad I didn’t send that angry support email to my web host. 🙂

Long Story Short…

Verizon FIOS is blocking outgoing (SMTP) email on Port 25. They’ve been rolling out this change since 2009 but apparently didn’t inform all of their customers. They say they’re doing it to reduce the spread of email viruses.

The “solution” is to change your SMTP port. Thankfully, many email providers (including mine) support Port 587 as an alternate SMTP port. Unfortunately, there will be some users who don’t have that option and are stuck not being able to send mail at all. Those unlucky folks will need to talk to their email provider or drop Verizon as their ISP.

If you’re having trouble sending mail using Verizon FIOS, check out the following links:

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