I'm a professional game developer from Wakefield, England, working as a senior programmer for Rebellion North.
I'm a married father of five and I a also sometimes do Retroburn stuff.
Martin 'Bytrix' Caine
Father. C++ Games Programmer. Cyclist. Guitarist.
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Email Deliverability
Monday, October 3rd 2011 / Blog

Identifying and Removing SNDS Spam Traps

As anyone involved in Email Marketing should know, even the most legitimate mailers can sometimes hit Spam Traps. Many people however don't understand what a spam trap is, and that's because there are two different types of trap which operate differently:

Honeypot Spam Traps
The first type of trap is an address specifically set up to catch email harvesters. The worst kind of spammers that scour the internet for any email addresses they can find to send their spam to. These 'true' spam traps are generally hidden away in the source code of websites, in the meta data of documents or in other 'hidden' areas where real people would generally not be looking. Bots (programs written to read a file or webpage and pull out all email addresses within the source) won't understand that some addresses are hidden and some aren't as they simply see them as text, within a large block of text. If these addresses receive email the person who created the spam trap knows the sender is sending to harvested addresses.

Hotmail Spam Traps
Hotmail spam traps are much more common and are how Hotmail reward senders that follow best practice (and some other ISPs and filtering companies use similar systems). However, even the most legitimate senders can have these spam traps in their database if they were lax with their bounce removals.

Most Hotmail spamtraps are old email accounts which are no longer active.

Say if you register for a new hotmail.com email address and don't log in to it. After a few months your account is de-activated but you have a grace period in which you can still re-activate your account. During this period you will still receive mail sent to the account.

After another few months and no re-activation, Hotmail will close your account. You will not be able to re-activate or log in to the account, and any mail sent to the address will bounce as a non-delivery.

This is the point where mailers following best practice will be clearing out their non-deliveries and removing the address from their database. All ESPs and major companies should be doing this as it's common practice.

A few months later, Hotmail will re-activate the email address as a spam trap. The owner will not be able to log in to their email and email sent to it will likely disappear, but the difference here is that you'll receive a 250 from Microsoft informing you of a successful delivery.

Of course, if you are monitoring your bounces you will have already ceased sending to the address by now anyway, but what if, for some reason you hadn't removed the email from your database?

Then you've sent to one of these spam traps and Hotmail knows you are not maintaining your list correctly.

The problem is even the most legitimate mailers might have less than perfect bounce management and might not remove these addresses. When you repeatedly hit such addresses you will then see your deliverability decrease and it can be hard to improve it again.

Hotmail aren't the only company using these type of spam traps but they are one of the main mail providers using them. They also supply a nice tool for senders called SNDS (Smart Network Data Services). What SNDS shows us, is volume of email sent to all Windows Live addresses on each particular day, it also shows us how many spam traps we hit and the time of the first and last spam trap hit (down to the nearest minute).

The data provided by SNDS can be used to identify the spam traps you are hitting and help you remove them from your database. I have recently run through a good few million Hotmail addresses to identify potential spam traps from within the data. This data was all collected via sign-ups to a website over the past 8 years, but in the early years the bounce management was limited and some spam traps made their way into the list. For the past 5+ years the list has been cleaned correctly, but still contained these old spam trap addresses as they appeared to be good from the SMTP logs.

I have now managed to remove every single spam trap from the list, with SNDS now showing 0 trap hits.

This is very much a one-off process, if you are a legitimate mailer who has a problem with SNDS trap hits it's likely you have some old data which was not cleaned correctly. So long as you are processing and removing bounces correctly now you should never get another such spam trap added to your database.

I'm not going to go in to detail about how to identify and remove the traps as that should be fairly obvious if you look at the data SNDS provides, but if you're reading this (and it's likely you have a spamtrap problem) then please feel free to get in touch and I might be able to help you. You can contact me using the icon links at the top right of the page.

If you found this post helpful please leave a comment below:
Diego / 2012-08-08 16:17:36
Hi Martin,

I have found this post very helpfull, I the developer manager for an email marketing software tool and I have found the same issue as you describe.

I have posted all our IPS in the Microsoft SNDS system.

I will like to minimize the traps hits that we have, so if you can share or point me in the direction you took to solve the problem I will appreciate it.

angel / 2012-08-16 12:55:31
Hi Martin

Thanks for the post.
Any company in UK that could clean up an email database from spam traps???

Chris / 2012-10-09 15:42:30

I am not seeing how the data that SNDS shares can help someone identify a spam trap. SNDS shows the entire email, including unmodified headers, for emails about which there were complaints only -- as far as I can tell.

But on days when SNDS shows 0 spam trap hits but that IP had complaints, we can see the entire message, including unmodified headers, that was complained about. Where else can I get this informaton from SNDS that could definitely identify spam traps? I'm at a bit of a loss as to where else I might look.

Thanks and Regards,
Floyd Arthur / 2014-09-25 15:05:36
Have a purchased bulk email list and need some guidance in producing a spam trap free list. Can you be of service ?
adrian / 2017-01-27 13:35:05
I like to thank you for sharing this important information. It would be great if you can share how we are find exact spam trap mails hit for particular ip .

kv / 2019-06-20 13:20:47
I have been looking at the time which is mentioned at SNDS, but in my mail logs I see lot of emails that are going to hotmail address, In those addresses how do I specifically know that this is a spam trap address ? Any suggestions or clues

Please help.

Thank you