Recent Posts

Tis the Season

A cartoon by twisteddoodles. An email says "you've got mail" and a human responds "what is it". <p>The email replies "a Black Friday sale" and the human asks "who?"</p></p> <a class= Read More

Yahoogle Requirements Update

Since I wrote about it last month the requirements for bulk senders to Yahoo and Google have changed a little.

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Can you STARTTLS?

Email supports TLS (Transport Layer Security), what we used to call SSL.

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Customer subdomain authentication

EDIT: Now with a production-ready implementation I talk about more here.

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Wildcards and DKIM and DMARC, oh my!

If you’re an ESP with small customers you may have looked at the recent Google / Yahoo requirements around DMARC-style alignment for authentication and panicked a bit.

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Deferrals at Microsoft

If you’re seeing a lot of “451 4.7.500 Server busy. Please try again later” from Office365 this morning you’re not alone.

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When Asking a Question

A lot of beginner questions about email delivery aren’t about broad strategies for success, or technical details about authentication, or concerns about address acquisition. They’re something like:

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New Requirements for Bulk Senders

UPDATE: You need to authenticate with both DKIM and SPF.

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Validity Charging for Feedback Loop Emails

History

Return Path was a major driver for the establishment of Feedback Loops (FBLs) back in the mid to late 2000s. They worked with a number of ISPs to help them set up FBLs and managed the signup and validation step for them. In return for providing this service to senders and receivers, they used this data as part of their certification process and their deliverability consulting. Return Path had a strong corporate ethos of improving the overall email ecosystem that originated from the CEO and permeated through the whole organization.

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The trouble with CNAMEs

When you query DNS for something you ask your local DNS recursive resolver for all answers it has about a hostname of a certain type. If you’re going to a website your browser asks your resolver for all records for “google.com” of type “A”1or “AAAA”, but that’s not important right now and it will either return all the A records for google.com it has cached, or it will do the complex process of looking up the results from the authoritative servers, cache them for as long as the TTL field for the reply says it should, then return them to you.

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