Spam Resource: All Things Deliverability

How many people are still using Post Office Protocol (POP, aka POP3) to retrieve their email messages nowadays? And how many people were using POP to pull mail from an external …

The other day I found myself watching "Down Cemetery Road," a show on Apple TV based on a Mick Herron novel (yeah, the Slow Horses guy -- and the jury's still out o…

If you spend any time on social media, you undoubtedly saw the dire warnings. It was all over Reddit , and there were a wealth of news articles and hot takes posted. Folks were i…

I just found something very interesting, when poking around in DNS: Google seems to have recently updated what goes into their " _spf.google.com " SPF record. Keep in …

I'm sure you've heard the opinions already: Open rate tracking is absolutely useless. Open rates are a garbage metric. Open triggers attract only bots talking to other bo…

The Messaging, Malware and Mobile Anti-Abuse Working Group (M3AAWG) is an industry group focused on keeping messaging ecosystems safe from threats like email spam, phishing, spo…

For a recent Valimail Ask Al video , I brought in Scott Ziegler , Valimail's VP of product, to share some real world results showing the actual benefits seen by a Valimail cl…

It's time to define another email technology-related term for the DELIVTERMS series here on Spam Resource. Today, what we'll explain is SMTP AUTH, short for Simple Mail …

Hey, remember when I told you that V1 of Google Postmaster Tools was going away? Not so fast... Turns out Google has changed its mind, at least for now. Fellow deliverability exp…

Here's a confusing rejection that an email sender asked me about the other day. It's a Microsoft OLC (Outlook Consumer, aka Hotmail or Outlook.com) rejection, authenticat…

As of November 3, 2025, Google has added a new warning to their Bulk Sender Guidelines FAQ page, warning that enforcement "ramps up" beginning this month. The warning:…

In my last post , I talked about what DMARC doesn't do. What it cannot do, addressing limitations and mis-assumptions. But, as I said then, I am a DMARC fan. I don't thin…

Let me be clear. I am pro-DMARC. I think you should implement DMARC. It is a valuable part of email security best practices. But I want to be "eyes wide open" about it.…

Are you trying to send email and seeing it rejected with "Domain of sender address does not resolve" or "Unresolvable RFC.5321 or RFC.5322 from domain"? These…

Hey, retailers! Webinar alert. Retail email: a prime target for phishing and spoofing, with fake emails and fake receipts. Whether they be somebody spoofing your brand to sell kn…