Online Advertising
Open rates became only half-measurable once the major providers added privacy features. They remain steerable, through four levers that have nothing to do with the subject line.
The open rate is the best-known metric in email marketing and, for some years now, the least reliable. One major provider pre-loads images on its own servers, which reports an open without a human having seen the message.
Depending on that group's share of your list, your reported open rate runs 15 to 30 per cent above the true one. That is no reason to abandon the metric, but it is a reason to read it only over time and never against industry benchmarks.
Two other numbers are more reliable: click rate as a share of all recipients, and the proportion of addresses that did anything in the last 90 days.
The sender name sits on the left in the inbox, is read first, and decides opens more often than the subject line does.
| Sender form | Effect |
|---|---|
| Company name | neutral, interchangeable |
| First and last name | personal, good for advisory work |
| First name from Company | the best combination in most tests |
| info, noreply, newsletter | the worst variant |
The last point is unambiguous: a sender address that cannot be replied to lowers open rates and deliverability at once, because replies are a positive delivery signal.
The preview text is the line after the subject. Leave it unset and the mailbox shows the first text in the message, often "View this email in your browser". That line costs opens.
Set it deliberately as a complement, not a repeat of the subject. The subject creates curiosity; the preview text supplies the argument.
Inactive addresses hurt twice. They depress the open rate arithmetically, and they depress deliverability in fact, because mailbox providers read inactivity as a signal.
A proven rhythm: every six months identify addresses that have not opened or clicked in 180 days; send a two-message reactivation sequence with a clear question; remove non-responders from the regular send; delete after a further 90 days.
Firms resist this because list size falls. But the relevant number is not list size, it is the number of people reading.
The widely quoted best send times are averages of other people's lists and meaningless for yours. Establish your own: send at four different times over twelve weeks and compare click rates, not open rates.
In practice the answer often surprises. B2B lists frequently respond Tuesday to Thursday mid-morning, retail lists at weekends, trade lists early in the morning before work starts.
The subject is the most optimised and least effective lever. Three robust observations: 30 to 50 characters display fully on phones; first-name personalisation is slightly positive in warm lists and negative in cold ones; questions and numbers work better than statements, but the effect is in the low single digits.
In B2B 25 to 40 per cent, in retail 15 to 30. The direction over six months matters more than the level.
Better every two weeks reliably than irregularly often. A fixed rhythm creates expectation, and expectation creates opens.
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