What is sender reputation?

The inputs you control before sending are the ones that matter most: hard bounces, complaints, and whether recipients open and reply. One campaign to a stale list can move reputation in a single send and take weeks of clean sending to recover.

Reputation attaches to both the IP and the domain. On a shared IP you inherit some of everyone else's behaviour; domain reputation follows you whichever IP or platform you use.

Verification is the most direct lever because bounces are the one input you can remove entirely before a send rather than manage afterwards.

Reputation is judged per provider. A sender can be fine at Gmail and struggling at Outlook.com at the same time, which is why problems often show up as one provider's bounces or deferrals rather than across the board.