I have just received an email with a question about SE Linux that was re-sent due to the first attempt being blocked by my anti-spam measures. I use the rfc-ignorant.org DNSBL services to stop some of the spam that is sent to me.
The purpose of rfc-ignorant.org is to list systems that are run by people who don’t know how to set up mail servers correctly. But the majority of mail that is blocked when using them comes from large servers owned by companies large enough that they almost certainly employ people who know the RFCs (and who could for a trivial fraction of their budget hire such people). So it seems more about deliberately violating the standards than ignorance.
The person who sent me the email in question said “hopefully, Google knows how to make their MTA compliant with RFC 2142“, such hope is misplaced as a search for gmail.com in the rfc-ignorant.org database shows that it is listed for not having a valid postmaster address . A quick test revealed that two of the Gmail SMTP servers support the postmaster account (or at least it doesn’t give an error response to the RCPT TO command that is referenced in the complaint). However Gmail administrators have not responded to the auto-removal requests, which suggests that email@example.com is a /dev/null address.
However that is not a reason to avoid using Gmail. Some time ago Gmail took over the role of “mail server of last resort” from Hotmail. If you have trouble sending email to someone then using a free Gmail account seems to be the standard second option. Because so many people use Gmail and such a quantity of important mail is sent through that service (in my case mail from clients and prospective clients) it is not feasible to block Gmail. I have whitelisted Gmail for the rfc-ignorant.org tests and if Gmail starts failing other tests then I will consider additional white-lists for them.
Gmail essentially has a monopoly of a segment of the market (that of free webmail systems). They don’t have 100%, but they have enough market share that it’s possible to ignore their competitors (in my experience). When configuring mail servers for clients I make sure that whatever anti-spam measures they request don’t block Gmail. As a rule of thumb, when running a corporate mail server you have to set up anti-spam measures to not block the main ISPs in the country (this means not blocking Optus or Telstra BigPond for Australian companies) and not block Gmail. Not blocking Yahoo (for “Yahoo Groups”) is also a good thing, but I have had a client specifically request that I block Yahoo Groups in the past – so obviously there is a range of opinions about the value of Yahoo.
Someone contacted Biella regarding an email that they couldn’t send to me . I have sent an email to Biella’s Gmail account from my Gmail account – that should avoid all possibility of blocking. If the person who contacted Biella also has a Gmail account then they can use that to send me email to my Gmail account (in the event that my own mail server rejects it – I have not whitelisted Gmail for all my anti-spam measures and it is quite possible for SpamAssassin to block mail from Gmail).
It turns out that the person in question used an account on Verizon’s server, according to rfc-ignorant.org Verizon have an unusually broken mail server .
If your ISP is Optus, BigPond, Verizon, or something similarly broken and you want to send mail to people in other countries (where your ISP is just another annoyance on the net and not a significant entity that gets special treatment) then I suggest that you consider using Gmail. If nothing else then your Gmail account will still work even after your sub-standard ISP “teaches you a lesson” .