Spam Resource: All Things Deliverability
I'm Al Iverson and I'm here to help. You've got questions about email deliverability? Find answers here! This is where I've been writing about email technology, sender requirements and best practices, email authentication, stopping spam, and more, for twenty-four years. And if you can't find an answer in one of the 1700+ articles here, drop me a line with your question, and I'll try my best to follow up. And don't forget to subscribe to my email newsletter, so that you'll get updated info pushed to your inbox weekly.
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Microsoft rate limiting issues?

Microsoft rate limiting issues?

Seeing rate limiting deferrals at Microsoft OLC (Outlook Consumer/Hotmail) domains ? Specifically with this error message: 451 4.7.650 The mail server [IP Address] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) If so, it might not just be you. Many email senders are reporting issues as of late, and Microsoft has updated their email sender support request form with this note: “We are aware of an issue that may result in c…

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The Latest Deliverability News

Microsoft rate limiting issues?

Seeing rate limiting deferrals at Microsoft OLC (Outlook Consumer/Hotmail) domains ? Specifically with this error message: 451 4.7.650 The mail server [IP Address] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postma…

Microsoft SNDS: It's alive!

Look what I just found in my email. It's an email from staff AT hotmail.com: You are receiving this message because your sender IPs are enrolled in the Junk Mail Reporting Program (JMRP). We are modernizing JMRP by rebuilding the service on a new platform. Going forward, pr…

FUD: CAN-SPAM and PO boxes

I saw somebody recently say that one of their biggest fears about starting a newsletter is that CAN-SPAM (the US federal anti-spam law) requires that you have an address in the footer and that it has to be legit, else you can (supposedly) get hit with a $50,000 fine. And also …

Newsletter Spotlight: San Diego Meteor

We’re starting a new feature here on Spam Resource: The Newsletter Spotlight! I’m a big fan of newsletters — they’re one of the best things about email — and I thought it would be fun to every so often highlight a newsletter that I’ve heard about, stumbled upon, actually subscr…

Fun with data: BIMI records in DNS (February 2026 Update)

Here’s a long overdue updated snapshot of BIMI sender logo DNS records as found in the top ten million domains data set (the domain list from host.io , where I query and log a bunch of DNS records for every domain, every month). By adjusting the view on my Wombatmail BIMI data…

Spam Resource Spotlight: Josh Nelson

Josh Nelson is the CEO of Civic Shout , an ad platform built to help progressive causes reach supporters who actually want to hear from them. Earlier in his career, Josh ran major email and digital programs for groups like Al Gore’s Alliance for Climate Protection and CREDO Mo…

Join me at Litmus Live 2026!

I’ll be co-presenting in a session at this year’s Litmus Live , peering into my crystal ball alongside Danielle Gallant and Guy Hanson from Validity. Join us for this free, virtual event! Our session on February 11th will see is sharing our thoughts on emerging trends, technolo…

Five Inbox Logos That Are Not BIMI

Every so often someone emails me a screenshot from their inbox and asks a simple question: Is this a BIMI logo? A lot of the time, the answer is no. In my latest Ask Al video for Valimail , I walk through five logo, avatar, and profile picture mechanisms that can look a lot lik…

SmarterMail exploit: upgrade now!

SmarterMail is an email/collaboration suite of tools positioned as a Microsoft Exchange alternative, offering native MAPI support, supposedly making it easy as a drop-in replacement for Microsoft's tools. If you use SmarterMail, it's important that you immediately ensu…

Guest Post: Spamtraps Aren't a Hygiene Problem -- They’re a Data Integrity Problem

Koli-Lõks provides visibility into bulk email traffic, tracking sending IPs and domains to show how email is sent and on behalf of whom, with a focus on ESPs, ISPs, and other large email sending platforms. The email traffic data they collect is used, for among other purposes, t…

SMTP rejections are up: One reason why might surprise you!

Ouch, what a click-baitey headline. But let’s run with it, because it comes from an honest place. As I mentioned here and elsewhere, I recently teamed up with Scott Ziegler from Valimail for a webinar digging into SMTP rejection data provided by Google starting in July/August …

From and reply to: Routability and matching domains?

Here’s a question that comes up enough that I’ve got multiple versions of it sitting in my blog scratchpad, just waiting for me to draft my thoughts. And I've got thoughts! Let me share those thoughts, just after sharing the the two main versions of this question that I'…

RNC v. Google Ninth Circuit appeal fails

Eric Goldman, writing for his Technology & Marketing Law Blog, has just shared an update in the RNC v. Google saga , this time the Ninth Circuit wastes very little time shutting the whole thing down. If you remember the earlier round, the Republican National Committee claim…

Spam Resource Spotlight: Chad S. White

Chad S. White is Group Vice President of CRM Strategy for Zeta Global. He is also the publisher of EmailMarketingRules.com , a blog and resource hub that serves as a definitive guide for marketers looking to master the complexities of email. Grounded in the frameworks of his cr…

When DMARC breaks: Failures fixed & other stories of support success

Webinar alert! Join me, Al Iverson, community and industry person her at DMARC provider Valimail for a chat on January 22nd talking through common ways DMARC implementations go wrong, why “doing it yourself” gets so tricky, and how hands-on, expert support can mean the differe…

Ask Al: January review and reset for email senders

You survived Black Friday. You survived Cyber Monday. You survived Q4 and 2025. Now what? In my first Ask Al video of 2026 , I walk through what January should look like for email senders once the dust settles. This is the window where you can safely review, fix, and plan witho…

Dead domain: worldnet.att.net

AT&T as an internet provider and mailbox provider has been around for a while, surviving through various iterations over the years. Once upon a time (starting in 1996) that was dialup internet branded as " AT&T Worldnet ," with customers being provided email a…

Gmail announces A.I. inbox: What does this mean?

In my recent “ 2026 predictions ” blog post, one of the things I touched on was Artificial Intelligence. I mentioned that while it was certainly a component of deliverability, it is mostly already driving spam filters in ways you’re already accounting for, so don’t really worry…

Ask Al: 18 Months, 61 Videos

Just around eighteen months ago, I started work on a new video series for my employer, DMARC provider Valimail . The goal? Answer an email related question, usually with a focus of email deliverability or email authentication, with a short video, every week or two. Thus, “Your …

Zeta: Q3 2025 Email Benchmarks

Looking for benchmark email marketing stats? Zeta Global’s got the data, and they’re not afraid to share . Benchmark data can be a bit of a mixed bag. It can be handy to use as a starting point to know if you’re doing anywhere near okay from a deliverability perspective, but br…

Wait, what is Microsoft SNDS? (for 2026)

Every time I post about changes to Microsoft SNDS, somebody always asks, “What, what is Microsoft SNDS? How do I use it?” And so, to be proactive this time around, allow me to link to this wonderful introductory overview and explainer from fellow deliverability expert, Iterable…

January 2026 Microsoft SNDS Updates (So far)

If you use Microsoft’s SNDS (Smart Network Data Services) online reputation portal to monitor for deliverability and reputation indicators for mail you’re sending to Microsoft OLC (Outlook Consumer, aka Hotmail/Outlook.com) mailboxes, you might have noticed this already. Clear…

Email Deliverability in 2026: What's next?

You’re wondering what deliverability changes await us in 2026? I’m so glad you asked! Let’s talk about deliverability in 2026: What’s here now, how things work today, how it’s all evolving, and what I think things will look like over the coming year. In 2026, Technical Complian…