Spam traps - What are they ?

A spam trap is an email honeypot and in its simplest form this is an email address that is used to collect spam emails. Unlike a spam filter however, it doesn’t try to recognise what is spam and what isn’t, it just assumes that everything it receives is spam. It can do this because the email address is never used by a real human being and has never been subscribed to receive any email. Hence anything that gets sent to the address is unsolicited email.

You can create your own simple but crude spam trap very easily. Create an email address and publish it on your website in a way that is invisible to a normal user. An automated harvester will come and collect the email address and eventually over time you will start to receive unsolicited emails. Spam traps of this type are very successful in identifying lists that have been harvested from WHOIS records of domain names, websites and Newsgroups.

Another type of spam trap involves taking a once valid email address and after a period of time converting it to a trap. Many ISP's such as Hotmail, Google and Yahoo adopt this approach with old and abandoned mailboxes that are no longer used. The addresses will normally be left dormant for a period. The exact length of time varies and is unclear but it is thought to be between 6 and 18 months. During this time the email address will normally return a bounce to indicate to non-spammers that the address is no longer in use. Hotmail might return an error such as “550 Requested action not taken: mailbox unavailable”.

Using list hygiene techniques the email address would be removed after a pre-defined number of bounces. Spammers generally won't remove the email address from lists because of a bounce so when the address gets converted to an spam trap they will continue to use it.

So how do you know if you are sending email to spam traps? This is something you want to know before your reputation is damaged and you suffer from deliverability issues. If you are using an Email Service Provider then it is likely they will monitor this for you and let you know if a list you are using is causing problems. If you are sending your own emails then some ISP’s have services that can help. Microsoft has the Smart Network Data Services (SNDS). This service tells you how many spam traps each of your IP addresses have hit and the complaint rate.

If you are hitting a number of spam traps then how do you remove them and avoid it happening again? As you would expect, the people that operate the spam traps are obviously reluctant to tell you which email addresses are spam traps and there is no way to visually identify a spam trap as it looks like a normal email address. Microsoft say on the SNDS FAQ page “We recognize that providing the actual trap messages would be useful to legitimate businesses trying to clean lists or customers that are hitting these accounts, however this is another unfortunate case where the risk of the data being useful to spammers is too great.".

The best way to avoid spam traps is good list hygiene and management. Always remove hard bounces after a number of failed delivery attempts and look at segmenting your data into engaged and non-engaged recipients. You should try and re-engage the users who aren’t opening or clicking on the links in your emails and if after a period, maybe 6 to 12 months, there is no activity then they should be removed from the list. If you do acquire new data then make sure you know the source of the data and don’t combine it with your existing lists until you are happy that the data is clean of spam traps.