Among the pieces of email marketing advice that circulate most persistently is the guidance on send timing. Tuesday and Thursday are good. Ten or eleven in the morning works. Avoid Monday mornings and Friday afternoons. These rules have been passed from guide to guide for fifteen years.

The problem is that the research base is narrower and more context-dependent than the advice implies.

Studies of aggregate email performance do find statistical patterns in open rates by send time. Tuesday and Thursday perform slightly above average. But the effect size is small — typically a one or two percentage point difference in open rates — not the dramatic swings the advice implies.

More importantly, aggregate data hides enormous variation by category. A newsletter for professionals who read it as part of their work routine performs very differently by send time than a promotional email to a consumer list.

The more productive framework is not "what time is best?" but "when does my specific audience have the attention and context to engage with this?"

A newsletter for home-based business owners may perform best at 6am, when they do their reading before the day starts. The same newsletter for corporate employees may perform best at 7pm. Neither matches the "Tuesday 10am" rule — but both are correct for their specific audience.

One consistently underreported finding: the impact of send time on click rates and conversion is smaller than its impact on open rates. A subscriber engaged enough to click through does so regardless of when the email arrives.

This means timing optimisation is a micro-optimisation on open rate for an audience that was already going to engage. It is not a lever for converting the disengaged.

Send time matters, but far less than content quality, subject line strength, and audience match. Test send times for your specific audience rather than following aggregate recommendations — and invest the time saved into improving the content itself.