A quick overview of Outlook.com (Hotmail) sender support


Over the past two months, I have taken on a role to deal with deliverability and user complaints for Outlook.com (Hotmail). The main areas of focus are reducing user spam complaints, and helping to streamline the process for senders when they get blocked from delivering to Outlook.com. This includes fixing bugs in the spam filtering process, but also fixing bugs in the SNDS portal.From time to time, people ping me and ask to get unblocked from Outlook.com. The majority of senders know the existing process (probably better than I do!) but here’s how it works.

I’m going to try to give enough information to be helpful, but not so much as to give too many clues to malicious senders about how to get around the process.

We consider it our primary responsibility to protect our users from spam, malware, and phish

Outlook.com has multiple filters including sender IP reputation, content filtering, machine learning (Smartscreen), feedback loops, and user personalization. When senders exceed a threshold in parts of those categories, they get blocked. This is in order to protect the service because Outlook.com is under attack from spammers every single day.

However, we understand that sometimes legitimate senders get caught up in our filters. That is why we offer a variety of Support tools.

a) Outlook.com expects senders to self-service and use these tools, and it is up to senders to ensure that they have best sending practices. They can use the Hotmail/Outlook.com SNDS portal to measure their deliverability: https://postmaster.live.com/snds/index.aspx?wa=wsignin1.0

b) There are third party organizations that can help in deliverability. One is the ReturnPath Sender Score Certified which helps in deliverability when on their good IP list. Another is 250 OK and while they don’t have an IP reputation list, they do help you manage complaints and bounces. Driving those down usually helps in delivering to all receivers, including Outlook.com.

There may be others but I can’t think of them off the top of my head. We may also add more good IP reputation lists in the future.

c) For Office 365 customers, make sure you set up SPFDKIM, and DMARC. For senders using Exchange on-premise (not Office 365) to send out email, I recommend that they install DKIM to add digital signatures to their outbound email. There is a DKIM agent for Exchange on GitHub, I haven’t used it but several other Exchange customers have and it works for them. https://github.com/Pro/dkim-exchange.

For all others, make sure your SPF, DKIM, and DMARC records are properly configured using whatever setup and infrastructure is supported.

This doesn’t guarantee delivery. But it can help (it certainly doesn’t hurt).

So what happens when you create a support ticket?

We understand that when senders create support tickets, they just want one thing and one thing only – to get unblocked. Or, sometimes people say “How do I get whitelisted at Hotmail?”

The answer is: There is no way to get whitelisted. Everyone goes through the same process. Even internal teams at Microsoft that want to send to Outlook.com have to do it. Even if you get on the ReturnPath IP reputation list, user personalization might still send messages to Junk.

You must create a support ticket using the SNDS/Postmaster portal to troubleshoot delivery. You can email me saying “Terry, my IPs are blocked! Help!” I’ll reply back saying “Please create a support ticket in the SNDS portal.” Everyone has to do that, even internal teams at Microsoft.

The Support process has multiple layers; there is some automation, a couple of layers of higher Tier Support, and then finally some Product Team support when required. Because of the overwhelming volume of support requests, and the fact that there are lots of spammers that try to game the support process, this is why we push so hard for people to use the self-service tools (the SNDS portal).

Once it gets through the support process, IPs are either approved for temporary blocking or throttling mitigation (i.e., IPs that were blocked will no longer be blocked [temporarily; if they generate poor reputation after a time limit they will get blocked or junked again]), individual sending limits may be lifted, or the request may be denied. I won’t go into the rationale for each of the decisions, but suffice to say, the Support folks do a good job such that we can scale the service given the volume of requests we receive.


That’s a brief overview of the Outlook.com sender support process. Hopefully you find it useful.


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