A follow-up email is a short message to someone who didn't reply to your first one. In cold email, many replies come from the follow-ups, not the first email: people are busy, and a polite second note catches them at a better moment.
How to write one
- Send it as a reply in the same thread, so the first email sits underneath.
- Keep it shorter than the first email: two or three sentences.
- Add something: a result, an example, a different angle, a simpler question.
- Avoid "just bumping this" or guilt ("I haven't heard back").
How many and when
Three follow-ups is a good default, spaced further apart each time: for example after 3, then 5, then 7 days. More than four starts to annoy people and raises spam complaints.
When to stop
Immediately when the person replies, even with "not now", and whenever someone asks to be removed. A tool that stops follow-ups automatically across all your mailboxes prevents the worst mistake in cold email: following up after a reply.