Mail bouncing from Hotmail (deliverability problems)

Are you experiencing deliverability problems with Hotmail? Are mails inexplicably bouncing? Well, you might be blocked. It happens to a lot of people, but don't worry, in this article we'll try to give you the main reasons and solutions to start delivering to your Hotmail-subscribers again.

Why does hotmail block my mails?

The main reasons why hotmail blocks your e-mail are:

  • Your infrastructure isn't configured properly
  • Your servers have a bad reputation
  • Your e-mail contains URL's with a bad reputation
  • Your content fails the content filters
  • Your activity scores are low or bad

Luckily, there's a lot you can do about this.

How to make sure your infrastructure is in order

Make sure you've correctly implemented SPF and SenderID. Next, make sure you've got DKIM covered. Set up Reverse DNS. You can test all of these with our reports.

How to improve your server reputation

A bad reputation is easily gained, luckily, you can do a lot to redeem yourself. First, are you enrolled in the Hotmail Junkmail Reporting Program?. No? Well, get in there as quick as you can. If you automatically unsubscribe people who don't want to be on your list, your reputation will improve quickly.
Second, make sure all your unsubscribe forms are in order. Are your mails already sporting a List-Unsubscribe header? Both Hotmail and Gmail support these and provide unwanting recipients a way to unsubscribe that they trust!
Third, make sure your servers support throttling, if you try to pound as much mail as possible into Hotmail at once and ignore their rate limits, you'll end up in the spambox or get dropped.
For more tips see: Improve your deliverability in three steps.

Your e-mail contains URL's with a bad reputation

This is bad, most likely, your URL's have ended on a blacklist, or have been involved in spam runs. Do some checks whether you're listed on major blacklists, and if you are, make an effort to be removed. If you want a quick fix, use a new domain, but change your practices. Our system checks major blacklists for your URL's.

Your content fails the content filters

This is the only part of the process that's black box. Of course, there are obvious no's, like free or viagra in a large font. Mails consisting of images only doesn't fare to well either. Valid HTML is important here.

How to improve your activity score

One of the latest weapons in the arsenal of spam fighting is user activity. The concept isn't that complicated, for every user action your domain or your server gets points. If someone marks you as junk, it's bad (unsubscribe them!), if they mark you as 'not junk', it's good. If they spend time reading your mail, it's good, if they click, it's even better.
Don't get tempted to manipulate this score with a lot of proxy accounts, because Hotmail already has monitoring in place for that.
One of the best ways to improve your activity score, is to use read- and clicklogs to determine subscriber activity. If you remove everyone who's been inactive for a while, your total activity score improves a lot. As a side bonus, you'll no longer pay for mailing people who ignore you.
Another reason for frequent list purges, is the removal of spam trap addresses. Those are really old addresses that have inactive for a long while and have been converted into a tool for catching spammers.

Bonus tip: Hotmail Smart Network Data Services

Are you already monitoring your servers in Hotmail SNDS? No, well, get at it. SNDS is a great way to monitor your deliverability to Hotmail. You can see whether your mails are being accepted on a day by day basis and identify problematic servers.

Other things you can do

We recommend doing a free deliverability report to identify any other problems within your mail. Below are references to more detailed information, consider reading those as well.