Developers often attack this problem: "How can I do everything (DomainKeys and others) so that the message does not get into someone's spam box?"
I worked on a website that emailed 20,000 users weekly.
The key point in eliminating spam boxing - besides all the technical components described in the link above posted by Martin - is to make sure that your recipients are not spam - whether you can.
Bayesian detection algorithms on mail servers provide source data from users who click "this is spam" in their mail clients, so if your users consider you to be SPAM, you will receive lower delivery interest rates (be prepared: 100% impossible).
- From:. , , , . " " , - , , . UP FRONT .
( !). " ", , , . , .
. . , , . " " ", " , , .
, , , (, ..). , , . , "" - , .