Follow-ups: delays & threading

Control timing and whether follow-ups stay in the same thread.

1. 01Set Wait X days between steps (3–4 days is a good default).
2. 02Toggle Same thread to send follow-ups as replies with Re: subject.
3. 03Same-thread keeps context and usually lifts replies; new-thread gets a fresh subject test.
4. 04Delays count sending days only — your schedule's off-days are skipped.