I use Verizon FIOS as my home ISP. I like it , it’s very reliable and Verizon is very responsive to my problems. Recently, when I reply to emails, their server, outgoing.verizon.net won’t send the email. It rejects it with a 5.7.1 notice and calls it spam. I can sympathize why do this. Verizon like every other ISP, doesn’t fully trust their customer base and SPAM is a scourge on the world’s email infrastructure.
Why does this happen? Apparently they generate a signature and if this signature looks like a spam payload they will reject the email.
So why don’t I use someone else to send email? On all of the home ISPs port 25 is blocked except your local authorized email server. On Verizon port 25 is not used. Their SMTP port is encrypted and appears on port 465. Of course if you have a vpn tunnel to somewhere else (i.e. work) you could use their mail server but I don’t have that luxury so I am stuck with what Verizon provides. This is not an exhaustive list. There are a lot of ports that could be used but the common ones are 25, 465 and 587.
<Sigh> However </Sigh> I just wish Verizon would give me the benefit of the doubt. I am using an encrypted connection to their SMTP server with a Verizon assigned username/password. They know who is sending the emails. (Email headers can be easily forged but the encrypted connection is harder to hack). I wouldn’t mind being in their good graces until someone complains about me.
At least they have a work around. Namely you send the email to: email@example.com
as the *only* recipient and wait 30min-1hour and they will put this email in a whitelist. You can resend the email after than and it won’t get bounced.