Warm-up is an observation process, not a fixed calendar. Volume should increase only when real feedback supports the next stage.
Make the audience the first control
Begin with recipients who clearly requested the messages and have the strongest recent relationship with the sender. A technically perfect schedule cannot compensate for purchased, stale or unclear-consent data.
Increase from evidence, not dates
Review deferrals, permanent failures, complaints and engagement before each change. Different mailbox providers may require different pacing and investigation.
Document pause and rollback conditions before launch so commercial pressure does not override warning signals.
Keep identity and volume stable
Avoid changing domains, From identities, content patterns and traffic sources at the same time. Stable inputs make provider responses easier to interpret.
No warm-up plan can guarantee inbox placement; it only creates a disciplined way to observe and manage risk.