Email sequence
An email sequence is a planned series of emails sent to one prospect with waits between steps, which stops when the person replies.
A sequence is the set of steps you plan for each prospect: a first email, then follow-ups after set waiting times. Each step can have its own subject and text. A good sequence ends for a prospect as soon as that person replies, unsubscribes or bounces, so nobody gets a follow-up to a conversation that has already started.
Most cold sequences have three to five emails, spread over one to three weeks. More steps bring more replies but also more complaints, so the right length is a trade-off for your market. Give each step a new reason to answer. Repeating the first email in different words is weak.
Common mistakes: no stop on reply, all steps sent at the same time of day, a wait that is too short, and the same message in every step. Plan the whole sequence before you launch, preview each step with real data and check how long the full sequence runs from first send to last.