Email advertising statistics: what they measure, and what they leave out

28 August 2026 · 1 min read · The Bulk Mail team

The best-known email advertising statistic is a return-on-spend figure that has been quoted for years, usually without its methodology attached. It is not fabricated — but it measures something narrower than the way people use it.

What a return figure usually includes

Almost always: revenue attributed to email campaigns, divided by the cost of the email platform. Almost never: the labour to write and design the campaigns, the cost of acquiring the list, or the revenue those customers would have produced anyway through another channel.

Email looks extraordinary on that arithmetic because the denominator is small — the platform fee is the cheap part. That is exactly why the figure is quoted, and why it does not transfer to your budget without adjustment.

Attribution is doing most of the work

Most email attribution is last-touch within a window: a purchase within some days of an open or click is credited to that email. Widen the window and email’s measured performance rises without anything changing in the world. When you read a headline number, the attribution window is the assumption you should ask about first.

A statistic with no stated attribution window is a marketing claim, not a measurement.

How to build your own version

• Count all costs, including the hours spent producing the sends.
• Fix an attribution window before you look at the results, not after.
• Separate existing customers from new ones. Email is usually strongest at retention, and mixing the two flatters acquisition.
• Compare against the channel you would otherwise fund, not against zero.

The one-to-one exception

None of this arithmetic applies to individual email, where volume is low and each message can be worth a great deal. There the question is not return per euro of platform spend but whether an important message was read, and when. That is a tracking question, not a statistics one.