Quote:Bulk e-mail doesn’t have to be evil. Sometimes, it’s even a business necessity. How else does one urgently notify all clients about a sudden problem? Or send a conference agenda to all participants? But ever-vigilant spam filters can’t always distinguish a bona fide bulk mailing from spam. Sometimes paranoid filter settings are to blame, but more often, the problem lies in the message itself. This post explains how to send messages that won’t get flagged as spam.


For a message to get through a spam filter, it must meet several criteria. First, it must be technically perfect. Second, its content must be clean. And third, it needs an unblemished reputation. Let’s examine in more detail what this means.


Technical headers

The Multipurpose Internet Mail Extensions (MIME) standard, specified in several linked RFC memoranda (request for comments, which ultimately turns into a de facto standard), describes how to send various types of data (text, executable, graphic, multimedia files) by e-mail. Messages must strictly comply, and in particular, they must include mandatory fields. Those fields being empty or incorrect is bound to trigger a filter.

Full reading: https://www.kaspersky.com/blog/how-not-to-be-spammer/25218/