Sending legitimate commercial emails and avoid getting blacklisted or marked spam

Question

First of all

Around this world there are lots of people that lawfully and legitimately contact people via email to send commercial newsletters, and there are also lots of developers who work for these people and that are requested that only a short percentage of these lawful and legitimate messages go trashed by an email server like Gmail.

Also, I already know that spammers VS honest emailers is a cat-versus-rat race, and is continuously evolving.

That said

I would like to ask if there are any useful techniques, other than those I already know, that allows the owner of a large email addresses database (all with opted-in consent) to programmatically send advertisement to them and avoid getting blacklisted or just trashed at the very first time

Some useful techniques

are for example

• Implement Hashcash in the code. This dramatically slows the rate at which messages are sent (so this may require some cloud resources and mostly important asynchronous processing) but at least proves that about 1 second of CPU time has been "lovely dedicated" (let me say that) to composing that email
• Implement and enforce Sender Policy Framework in its most restrictive ways. This (if implemented on the recipient side) assures that all emails from a specific domain come only from mail servers under the domain owner's control. But AFAIK while a few servers use a violation of SPF as an excuse to reject a message, those don't count the fullfillment of an SPF as less spam probability (because it's so cheap to register a domain a spammer can daily buy and configure lots)
• Clearly mention opt-out procedures in the text by also explicitly specifying the word unsubscribe in the text, because some filters count that word as legitimate
• Implement DKIM signature, because I found that a very high percentage of mail just not DKIM-signed is deterministically marked spam by Gmail. DKIM doesn't offer much more assurance than SPF but DKIM-signed mails can be relayed

Any other technique to suggest? I understand that the topic may evolve in the future

Answer 1

I can think of two third party services that will take care of the leg work required to send volume email and also remove the burden of protecting against being classified as spam.

Amazon Simple Email Service (SES) allows you to send large amounts of email using web services. They already implement DKIM and you can begin sending to the masses after you have registered out of their sandbox period.

You could also use a service like Mail Chimp. They offer an API and are specifically geared at sending volumes of email. See their page on deliverability.