Blog Post

Stop Spreading The Christmas Joy!

We all know that email marketing activity heightens in the lead up to Christmas, but I’m not telling anyone to stop their Christmas campaigns. Don’t be crazy! Christmas is an excellent opportunity for marketers, even if it is just to wish everyone a Merry Christmas!  But, as a result, ISPs have gone to DEFCON 1 and restrictions on IP addresses are pretty tight. Toight, like a tiger!


A common logical response is: “Well, if I can only send this much with a handful of IP addresses, why don’t we send using a truck load of IP addresses?”

There are ISPs that limit the number of emails that can be sent from a particular IP address in a given period of time. ISPs do this to help manage their inbound servers and avoid delays in service due to bottlenecks. So it does seem to make sense to spread volume over many IPs to increase the rate in which you can send. Even though, this isn’t exactly helpful from the receiving end as the sender has just circumvented the initial function of IP rate limiting.

Hotmail is notorious for actively rate limiting senders.  However, they have a smarter and more reasonable rate limiting metric based on sending reputation.  This allows them to prioritise mail streams that have proven to be valuable to their customers and delay or defer anything that has had a poor response in the past. Other factors that also affect this rate are the volumes in which the IP has previously been seen to send, the recipients it previously sent to and the consistency of sends.  If no history is present then extreme caution is the usual approach.

Adding more IPs to a sending pool can be useful if rate limiting by ISPs is causing serious business operational problems.  This is only effective if there are no other issues that are contributing to the throttling other than you have hit the maximum limit that the ISP is willing to receive from any IP address.  If this is the case then it is probably better to work with the ISP to make special arrangements for your mailing IP.  You’d have to be sending some pretty high volumes with exceptional engagement before this becomes an issue.

A good reason not to add more IPs to a pool is that Hotmail is pretty clever, they know when someone is trying to work around their anti-spam barriers.  And it’s not just Hotmail, this applies to most major ISPs as well as the millions of smaller ISPs or business mail servers that are part of a greater anti-spam network like CloudMark’s Global Threat Network.  Running the same mailing through several IPs will make you look like a snowshoe spammer, just have a look at The Spamhaus Project, it has a separate component that deals directly with this behaviour. 

Spreading volume over IPs to “stay under the radar” just doesn’t work in this day and age of big data.  Ultimately, how the recipients interact with an email is the purist metric an ISP can use, and it is this that will proliferate through all other reputation metrics.  Adding more IPs to a mail stream with reputation related rate limitation will only exacerbate your problems.  This is directly related to what anti-spam entities are calling email fingerprints or signatures.  These are identifiers that help correlate spamming behaviour in an effort to prevent future SPAM (Another topic for another time, perhaps).

If you are looking for ways to avoid anti-spam measures, then you might find this writing on the wall:
To count, to count, to weigh, to divide.
The ISPs have numbered your complaints and will bring them to an end.
You are weighed in the balances of anti-spam software, and are found wanting.
Your emails have been divided, and given to CloudMark and Spamhaus.


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