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Never too busy to talk about Microsoft blocking


I’m busy as a bee this week, with so much going on with work (and outside of work), that I’ve not been able to update the blog as much as I would like to.

But, I can spare a few minutes to talk about helping a client out yesterday, connecting with them just after he running their first inbox tests and sharing understanding on how to interpret the deliverability results. We walked through this snapshot data showing what it can show, with an eye to identifying difficulties. This time around, like is so often the case, Microsoft was the main problem/focus area found. No mail delivered means they’re probably blocked at Outlook.com/Hotmail.com (but not Office 365). Even before the client checks for the text of bounce messages in their sending platform, we know that they're going to look like this:

550 5.7.1 Unfortunately, messages from [x.x.x.x] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [#.eop-nam02.prod.protection.outlook.com]

So, off to the unblocking form they go. They're on a dedicated IP address and it sounds as though they haven't fully completed IP warming, so I suggested that they request pre-emptive accommodation from Microsoft, which is the magic phrase to explain (in Microsoft language) that the client is going through IP warming. They'll usually respond asking you to map out volume over the coming days and weeks, to allow them to set rate limiting (speed and amount of mail they'll allow) appropriately throughout that time.

As I told the client, and I'll tell you: If you're blocked at Microsoft, but nowhere else (or almost nowhere else), you're not alone. Microsoft filtering is more aggressive than that of the other largest mailbox providers. Sometimes that might mean just pushing through the pain and once Microsoft unblocks you'll probably be fine, but other times that might mean implementing special segmentation and perhaps a focus on engagement just for mail sent to the common Microsoft domains. (And if you do decide that special segmentation is the way to go, you can find a list of all the Outlook.com consumer domains I know about as part of the MAGY data here. Also, if you're struggling with Microsoft deliverability issues and want to read more on the topic, find my Microsoft deliverability guide here.)

Nothing too exciting; just a typical day in the life of a deliverability consultant.

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