Here's one I hadn't seen before. A sender was hitting this deferral when trying to deliver mail to Microsoft (Hotmail/Outlook.com) domains: smtp;451 4.7.652 The mail server [x.x.x.x] has…
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In my latest Valimail Ask Al Video , I walk through four specific email authentication failure scenarios, things that could trip you up when sending email to Microsoft recipients…
By now, you've probably heard: Microsoft has officially joined the club. Following in the footsteps of Google and Yahoo, Microsoft has announced new requirements for high-vol…
Here it is, the 2025 Spam Resource MAGY (Microsoft, Apple, Google, Yahoo) Bulk Sender Compliance Guide. This contains almost everything you need to know (I think? I hope?) about …
Microsoft’s Outlook.com or OLC (Outlook Consumer) email platform, the mailbox provider formerly known as Hotmail, can be a tricky one when it comes to managing and mitigating del…
Here it is, the first episode of "Fun with Data" for 2025. Today, I present to you a link to a downloadable list containing the top Microsoft Outlook.com (Microsoft OLC…
Did you know that Microsoft Outlook.com and O365 emails include special headers that break down the spam filtering results for email messages? These headers can help you decode t…
Who hosts what mail? MBP Spotlight is the new series here at Spam Resource where I’ll share ranking data for the top mailbox providers (including B2B!) based on where they fall…
Are you tying to send mail to users at Microsoft OLC domains like Outlook.com and are receiving rejections back that look like this: 532 5.3.2 STOREDRV.Deliver; Missing or bad ma…
Bounce message. SMTP rejection. Deferral message. Non-delivery report (NDR). 5xx error. 4xx error. No matter what you call them, there are a zillion different kinds of them out …
It's time for another entry in the DELIVTERMS dictionary! Today, let's define JMRP. JMRP is the " Junk Mail Reporting Program ," the mechanism by which email s…
Microsoft's SNDS (Smart Network Data Services) , the reputation portal that provides deliverability feedback for folks sending to Microsoft Outlook.com/Hotmail, appears to ha…
When sending to Microsoft OLC (Outlook Consumer - i.e. hotmail.com, outlook.com, msn.com, live.com, etc.) domains, are you seeing this bounce message? Microsoft: 5.4.4 (unable to…
Looks like Microsoft has run into email authentication issues today. Specifically, the domain hotmail.com appears to have a broken SPF record wherein messages sent by Hotmail/Out…
Starting on August 16th, Microsoft seems to have stopped sending feedback loop reports. Microsoft's FBL is called the "JMRP" (Junk Mail Reporting Program) and multi…
If you're seeing intermittent DKIM authentication failures at Microsoft domains (outlook.com, hotmail.com, etc.) -- meaning you're seeing "dkim=fail (body hash did n…
Microsoft OLC, aka "Microsoft Outlook Consumer," aka what used to be called Hotmail, now called Outlook.com (which includes the domains hotmail.com, outlook.com, live.…
Mashable's Tim Marcin and others are reporting that a failure in Microsoft's spam filtering has resulted in Outlook.com (Hotmail) users receiving a bunch of spam in the…
Check it out! It looks like Microsoft has updated SNDS to provide a bit more info than they provided previously. In the "Comments" column, they're now including sna…
