Why newsletter publishers should love hotmail and yahoo subscribers?

By Jennifer and Elizabeth

If you send out an email newsletter, open rates are always top of mind. The bane of your existence? The spam filter. And sometimes, the spam filter just goes a little crazy.

Let’s step back for a moment. How can you tell whether your email newsletter has gone to spam? The biggest sign is a sudden drop in open rate. If you have sent your email newsletter regularly for a while now, you likely know what your average open rate is. When you see that open rate drop, you’ve probably hit the spam filter.

One way to figure out if a spam filter has suddenly taken a liking to your newsletter is to look at open rates by domain.  Hotmail, Yahoo, and Gmail tend to be the 3 most popular email domains. Once you segment your open data by domain, it can be very easy to see whether you were hit with a spam filter or not.

Let’s take a closer look.  For the email newsletter below, we segmented the subscriber list by Hotmail, Yahoo, and Gmail subscribers.  

During this period of time, the list size was pretty stable.  There weren’t many new subscribers or unsubscribes.  However, it’s clear that Gmail dinged this newsletter at least 6 times over 2.5 months! Compare that to Hotmail, where open rates are a lot more stable, an  indication that the emails did not get eaten by the spam filter there.  

Let’s look at another publisher.  Again, similar pattern when broken down by domain.

Open rates for this publisher are a lot more stable for Yahoo and Hotmail readers. In fact, Gmail put this publisher in the doghouse for the month of September while Yahoo and Hotmail spam filters found nothing wrong with the newsletter.

These are just a couple of examples of specific publishers who have been dinged by Google, but across the board in our network, Google tends to be much more harsh with their spam filtering than Hotmail and Yahoo.  There is a significant difference in how your email is perceived by different spam filters.  And, it may just be that you’d prefer to have Hotmail and Yahoo subscribers.


  1. Hoi says:

    Easy way to segment the data if you are using mailchimp is to try their ‘Hairball’ tool. Let’s you create segments for yahoo, gmail, hotmail, aol etc. and compare them.

    • Elizabeth Yin says:

      Hi Hoi — yep, Hairball was a bit overkill for this experiment :) but for other experiments, definitely! This info just came from MailChimp’s regular analytics.

  2. Kevin says:

    Just wondering, since Microsoft has officially announced that by this summer it’s going to migrate all of Hotmail to Outlook.com, what kind of spam filtering patterns are you seeing with Outlook.com ?

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