A couple articles came out today talking about ISP requirements and how to find them.
EmailInsider talks about ISP best practices and how merely complying with CAN-SPAM is not enough to get good delivery at the ISPs.
Meanwhile, over at ClickZ, Stefan talks about what the ISPs want from you and how to find the information online.
Mark Brownlow links to a number of marketing and delivery blogs over at his website. Different perspectives and different thoughts will give you the tools to create the best email marketing campaign for your business.
Read MoreOver the last couple days multiple people have asserted to me that Yahoo is greylisting mail. The fact that Yahoo itself asserts it is not using greylisting as a technique to control mail seems to have no effect on the number of people who believe that Yahoo is greylisting.
Deeply held beliefs by many senders aside, Yahoo is not greylisting. Yahoo is using temporary failures (4xx) as a way to defer and control mail coming into their servers and their users.
I think much of the problem is that the definition of greylisting is not well understood by the people using the term. Greylisting generally refers to a process of refusing email with a 4xx response the first time delivery is attempted and accepting the email at the second delivery attempt. There are a number of ways to greylist, per message, per IP or per from address. The defining feature of greylisting is that the receiving MTA keeps track of the messages (IP or addresss) that it has rejected and allows the mail through the second time the mail is sent.
This technique for handling email is a direct response to some spamming software, particularly software that uses infected Windows machines to send email. The spam software will drop any email in response to a 4xx or 5xx response. Well designed software will retry any email receiving a 4xx response. By rejecting anything on the first attempt with a 4xx, the receiving ISPs can trivially block mail from spambots.
Where does this fit in with what Yahoo is doing? Yahoo is not keeping track of the mail it rejects and is not reliably allowing email through on the second attempt. There are a couple reasons why Yahoo is deferring mail.
The MAAWG Sender Subcommittee has published a Sender Best Current Practices document.
This document details what the current best practices in the sending industry are. Summarized the document says: