Here is a great article from ClickZ that outlines the rather complex chain of email deliverability. For anyone who has ever wanted to know all of the various steps involved in getting a message to a users inbox, this covers all of the steps. Check it out.

“Years ago, the e-mail delivery chain had just a few links. You loaded your e-mail and hit “send.” After a couple handoffs, the message arrived in your recipient’s inbox the way you sent it.

Today, that chain has many more links. Some block your e-mail, others help it along. Deliverability has become a big issue for many e-mail senders. It even spawned this column.”