Guide · the domain ramp
The weekly step is earned. Once a week the domain's last seven days are read, over every inbox on it, and a week with too many bounces holds the domain at its current number.
Under ten sends in the week, any bounce at all holds the domain. Four sends and two bounces is the loudest signal a warming domain can give, and a percentage of four means nothing. From ten sends up, the bounce rate has to be under your limit, 5% by default, for the domain to move. Under ten sends with no bounce is a clean quiet week, and it moves up on its own.
A held domain says so next to its row: held at week two, four of forty four bounced in seven days. The last seven days' sent and bounced counts are in the same table for every domain, held or not, so you see a bad week coming before the check does.
Read the bounces on the deliverability page before changing anything. A run of 5.1.1 means the addresses do not exist and the list is the problem. Run the free mail server check and clean it. A run of 5.7.1 means the receiver is blocking you for reputation or policy, and the fix is to slow down, check the domain's authentication, and let the week pass. The check runs again a week later, and a clean week moves the domain up as if nothing had happened.
A held domain keeps sending at its current number. What it loses is the step up. A domain whose inboxes bounce badly enough is a different matter: an inbox pauses itself when its own bounce rate crosses the line, and stays out of the pool until you re-test it.