Filtering adjustments at Hotmail

I’ve been seeing a lot of discussion on various fora recently about increased delivery issues at Hotmail. Some senders are seeing more deferrals, some senders are seeing more mail in the bulk folder. Some senders aren’t seeing any changes.
This leads me to believe that Hotmail made some adjustments to their filtering recently. Given some senders are unaffected, this appears to be a threshold change or a calculation change, tightening up their standards. The changes have been around for long enough now it does look like the filtering is working as intended and Hotmail is not going to roll these changes back.
So what can you do to fix delivery of mail that was good enough at Hotmail a few weeks ago and now isn’t?

  1. Look at your data hygiene. Do you have older addresses that haven’t responded in any way recently? Try removing that data from your mailings for a week or two and see if that improves your delivery.
  2. Check your content for URLs that might be advertised or spammed in mail from IPs other than your own. Use domains you have complete control over in all your mail, both for links and anywhere in the text.
  3. Contact recipients through a non email channel and ask them to add your address to their address book.
  4. Look at performance of your lists per acquisition channel, maybe one of your acquisition processes is giving you poor data. Removing these addresses may improve your overall reputation and get your mail into the inbox.

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Microsoft delivery partnerships

Last week John Scarrow from Microsoft made a public statement on Deliverability.com about Microsoft’s approach to using available products in the email industry.

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Content based filters

Content based filters are incredibly complex and entire books could be written about how they work and what they look at. Of course, by the time the book was written it would be entirely obsolete. Because of their complexity, though, I am always looking for new ways to explain them to folks.
Content based filters look at a whole range of things, from the actual text in the message, to the domains, to the IP addresses those domains and URLs point to. They look at the hidden structure of an email. They look at what’s in the body of the message and what’s in the headers. There isn’t a single bit of a message that content filters ignore.
Clients usually ask me what words they should change to avoid the filters. But this isn’t the right question to ask. Usually it’s not a word that causes the problem. Let me give you a few examples of what I mean.
James H. has an example over on the Cloudmark blog of how a single missing space in an email caused delivery problems for a large company. That missing space changed a domain name in the message sufficiently to be caught by a number of filters. This is one type of content filter, that focuses on what the message is advertising or who the beneficiary of the message is. Some of my better clients get caught by these types of filters occasionally. A website they’re linking to or a domain name they’re using in the text of the message has a bad reputation. The mail gets bulked or blocked because of that domain in the message.
One of my clients went from 100% inbox every day to random failures at different domains. Their overall inbox was still in the 96 – 98% range, but there was a definite change. The actual content of their mail hadn’t changed, but we kept looking for underlying causes. At one point we were on the phone and they mentioned their new content management system. Sure enough, the content management company had a poor reputation and the delivery problems started exactly when they started using the content management. The tricky part of this was that the actual domains and URLs in the messages never changed, they were still clickthrough.clientdomain.example.com. But those URLs now pointed to an IP address that a lot of spammers were abusing. So there were delivery problems. We made some changes to their setup and the delivery problems went away.
The third example is one from quite a long time ago, but illustrates a key point. A client was testing email sends through a new ESP. They were sending one-line mail through the ESPs platform to their own email account. Their corporate spamfilter was blocking the mail. After much investigation and a bit of string pulling, I finally got to talk to an engineer at the spamfiltering company. He told me that they were blocking the mail because it “looked like spam.” When pressed, he told me they blocked anything that had a single line of text and an unsubscribe link. Once the client added a second line of text, the filtering issue went away.
These are just some of the examples of how complex content based filters are. Content is almost a misnomer for them, as they look at so many other things including layout, URLs, domains and links.

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Getting removed from an ISP block

A question came up on a mailing list about how long it typically took to resolve a spam block at an ISP. I don’t think that question actually has a single answer, as each ISP has their own, special, process.
ISPA takes 5 minutes. You fill out a form, it runs through their automated system and you’re usually delisted.
ISPB asks a lot of questions in their form, so it takes about 15 minutes to collect all the data they want and 10 minutes to fill out their form. Then, using very, very short words you keep repeating what you need to the tier 1 person who initially responded. That person eventually figures out they can’t blow you off and throws your request to tier 2, who handles it immediately.
ISPC has a different, somewhat long form. Again, you spend time collecting all the data and then fill out the somewhat obscure form. You get a response, but it’s a boilerplate totally unrelated to the initial request, so you keep answering until you find a tier 1 rep who can read and do what you initially asked.
ISPD has a form that takes about 2 minutes to fill out. Unfortunately, it goes to an outsourced postmaster team in the Far East and response times are ranging from days to months right now.
ISPE has an email address and if you catch them on a good day, they’re very helpful. Sometimes there’s no response, though.
ISPF has a troubleshooting page and accept requests to fix things, but never respond in any visible manner.
ISPG they tells you to talk to Spamfiltering Company H.
Spamfiltering company H answers their email in a prompt and friendly manner. OK, sometimes the answers are just “wow, your client/customer/IP range is sending lots of spam,” but hey, it’s an answer.
Spamfiltering company I is a useless bag of protoplasm and don’t even answer the email address they give you on their webpages. In a fit of fairness, I have heard they will occasionally respond, but usually that response is to tell you to go pay some apparently unrelated company a bribe to get delisted.
Spamfiltering company J doesn’t have a lot of ways to contact them, but have a lot of folks that participate in various semi-public arenas so if you’re even slightly part of the community, you can email them and they’re very helpful.
Spamfiltering company K is totally useless, but will tell you to have recipients whitelist you.

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