Recent Posts

Undisclosed Recipients

To: Undisclosed recipients:;

Very occasionally you’ll see something in the To: header of an email that isn’t the email addresses you expect, instead it’s the string Undisclosed recipients:;. What does that mean?

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B2B Spam: Strapi, Unstructured and Reo

About a year ago I was rebuilding this blog, moving it from WordPress to … something else. I evaluated several content management systems for that, and one of them was Strapi.

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Domain Authentication

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Changes happen, even if you don't keep up

I cannot count the number of times I hear someone complain that they didn’t change anything and now their email isn’t delivering and why did this happen all of a sudden and how can they be blocked now when they weren’t blocked 3 months ago. Nothing changed, so why all of a sudden is mail failing?

an image of colored lights with the words 'Change The Only Constant' superimposed on them

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Laposte.net will be requiring all email be authenticated

Starting on September 9th laposte.net will begin requiring email to have valid, aligned authentication. Mail that isn’t authenticated will start to be delivered to the spam folder or rejected at delivery time.

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Yahoo's mailboxes are full

552 5.2.2 This message could not be delivered because the recipient’s mailbox is full. Please try again later or contact the recipient directly. See https://senders.yahooinc.com/smtp-error-codes#mailbox-full for more information

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Deliverability rules

Hot Take:

Anyone who has to know exactly what the rules are for inbox delivery is trying to figure out how close they can get to violating the rules without negative consequences. Senders that comply with the spirit of the rules don’t care what the specifics of the rules are.

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Message-ID Syntax

Our friends in the Email Geeks slack have recently started seeing sporadic rejections due to invalid Message-ID headers.

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Don't make your DNS TTLs too short

DNS is a complex, distributed database built on top of an unreliable network that spans the world.

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Gmail says your unsubscribe "Needs work"

Google postmaster tools dashboard with a “Needs work” message for Honour unsubscribe

Needs work?

We’ve written about RFC 8058 “one-click” unsubscribe and how it’s part of the requirements for bulk senders wanting to deliver mail to the major consumer mailbox providers.

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