I changed IP address in the last 18 months and despite great trepidation, was pleasantly surprised that deliverability was not degraded.
Paying a bond feels like protection money for something I think my domains/hosts already have: a good reputation.
I shall probably, with huge regret, hand over the delivery process to an external operator in the near future.
I haven't had any issues recently, but wonder... Are the failures still well-noticeable? I mean, when Gmail/Hotmail reject the letter - do they do it properly (SMTP 4xx/5xx rejection) or maybe they're now silently discarding it?
When I had the issues (even with large mail providers), my MTA had always generated me a bounce, and it had always contained something sensible and immediately useful - like a message that my DNS records got messed up or IP got in a blacklist. Every error message I saw contained links or clues to how the delivery problem could be resolved. Had this changed?
Ironport was selling mail filtering appliances. They also sold dedicated spamming engines that were whitelisted by the mail filtering appliances. This playing both sides of the street made them something of a joke, and they had to drop the spam engine business. They were eventually acquired by Cisco after that.
[1] https://groups.google.com/forum/#!topic/news.admin.net-abuse...
If you're sending mail, you're crazy if you don't get your sending mail servers added there. It's easy to do and helps prove you're not spamming.
I'm always amazed at how many people don't know about, or use in reputation checks.
So my point is, lots of anti-spam services check it, but few people sending mail make an attempt to get their server listed in there properly.
Mail Servers get listed in there automatically, but if you go in there and vouch for your mailservers properly you're get a more trusted ranking, which translates into a higher anti-spam ranking when checks are done.
Pricing in general isn't an effective strategy to stop this unless it becomes more prohibitive than the profit margins - and that's a very big number.
Actually, I'd love a good SMTP service that had a good reputation, but most of what's out there is more bulk-mail oriented. I just want to own my own domain and send email but not be beholden to gmail nor deal with deliverability headaches.
Let's say a remote mail server connects to mine to deliver an e-mail purporting to be from example.com (your business, which has an EV SSL/TLS certificate for the example.com web site).
The first thing to be done is to somehow verify that the mail is legitimately being send by the company. The best way we have to do this presently is via SPF and DKIM. We query DNS and the IP address of the remote mail server is listed in the TXT RR, so the SPF check passes. We query DNS for the key that the mail is DKIM-signed with, and that passes.
Now what? At minimum, we have to do another DNS query for the A RR for example.com, establish a TLS connection to example.com, retrieve the presented certificate, verify the certificate is valid (date, hostname match, etc.), verify the certificate is chained to a trusted root, and -- somehow -- check that the presented certificate is an EV cert. I don't know enough about EV certs to know if there's an easy, programmatic way to verify that a cert is EV vs. DV, etc., but let's assume that there is. There's also revocation/OCSP, etc., checks to be performed. And so on...
What you're proposing might work. That is, a company with an EV cert is probably unlikely to be sending out blatant spam, but I don't know of any existing tooling to do these types of checks. If it existed and were easily integrated, I would at least be willing to test it and see what the real-world results were (and it would be much more likely to become an acceptable tactic to use for distinguishing spam from non-spam). A plugin for amavis and/or SpamAssassin would probably go a long way towards making this happen.
All that said, do CAs publish lists of EV certs? It would be relatively easy to import a list of domains with valid EV certs and then say "if mail from one of these domains arrives with a valid DKIM signature, assume it is not spam".
Is it commercial email?
Or are you just interested in sending email to friends and family?
In the case it's both, which one is more important to you?
I have this idea for a "bonded email server". The idea is that smaller senders would pay a bond (say, $200) plus a small monthly fee to a bonding company, which has a trusted relationship with Google, Yahoo, Hotmail, etc. The bond ensures that you won't send spam through your mail servers and in exchange, the big hosts agree to whitelist the mail you're sending. After some period of time, you get your bond money back if you've been true to your word. You'd still pay your small monthly fee to the bonding company.
The database of "certified good" hosts could be maintained by means of DNS run by the bonding company.
The problem with the idea is that there's so little incentive for the big mail hosts to accept email from small senders. They'd much rather you use a Mailchimp for bulk sending and their own service (or one of their large competitors) for individual sending because they know that these are reliable partners.