Send more email to improve your delivery rate

Sounds odd? However the delivery rate goes up if you send more email. I noticed that companies sending very regular email have higher delivery rates than those that send infrequently. There is a simple logic why this happens, which I shall explain with an example of how delivery rate can be increased from 98% to 98.75% by sending more.

The delivery rate as commonly defined by many ESPs is:

Delivery rate = (Emails sent – emails that didn’t bounce)/(Emails Sent)

If your ESP doesn’t use this, it won’t be much different. You could think of delivery rate as the didn’t bounce rate, or acceptance rate, as proposed by the DMA EEC metrics standards project S.A.M.E

There are two main types of bounce, permanent and temporary. Also commonly called hard bounce and soft bounce.

By a long way the most common cause of a hard bounce is the user has terminating their email address, that is closing their account.

Assume that the number of users who terminate their email address each month is a realistic 1%. Then it follows that if you email once per monthly, each month you can expect to get 1% hard bounces.

As the number of email addresses being terminated has nothing to do with you or your campaigns then the monthly number does not change if you say send weekly campaigns. Just because you send more, it won’t cause more users to terminate their email address.

What will happen is that on each weekly campaign you will see a fraction of the 1% become invalid. If you are sticking to good list hygiene and removing hard bounced addresses then the number of hard bounces on each weekly campaign falls to 0.25%.

Unlike hard bounces, soft bounces are more liklely to be consistent regardless of campaign frequency. So in this scenario if we take the soft bounce rate at 1% then emailing monthly will give a delivery rate of 98%. That’s 100% – 1% soft bounces and 1% hard bounces. Whereas emailing weekly will increase the delivery rate to 98.75%. As the hard bounce component drops to 0.25%.

I’m not suggesting you should send more email to improve your delivery rate. There may be other reasons to increase your email, this is not one of them.

The takeway is that even seemingly simple metrics can be mis-understood. With all metrics you will get more value from them if you understand the factors that impact them. Imagine comparing your delivery rate to that of someone with a very different send frequency.

A final note, bounces can be used as a defence mechanism to spam. If you are emailing at least a couple of times a month and your delivery rate is below 95% then you have a data management issue or reputation issue.

In my next post I will look at how click rates can be impacted by frequency and how you could draw wrong conclusions.