What is Warmup network?
The pool of real, warmed inboxes that a mailbox exchanges warmup emails with; bigger and more genuine pools produce more natural engagement signals.
Warmup only works if the inboxes on the other end behave like people: opening, replying, moving mail out of spam. A warmup network is that set of counterpart inboxes. Networks made of other customers' real business mailboxes look like ordinary correspondence to providers; networks of throwaway accounts can be identified and discounted.
Every warmup message should also be tagged so it can be kept out of the reply queue and filtered from a forwarded inbox.