Sending Reputation Decay

Definition

Sending reputation decay is the gradual erosion of a sender's trust score when no email is sent for an extended period. Mailbox providers continuously evaluate sender behaviour, and a sender that goes silent for weeks or months loses the benefit of recent positive engagement signals — opens, clicks, replies — that previously supported inbox placement.

When sending resumes after a long gap, the provider treats the first campaigns with heightened scrutiny because the sender's behaviour pattern has become unpredictable. This is one reason why re-engagement campaigns sent to long-inactive lists frequently land in spam.

How Decay Works

Reputation algorithms assign more weight to recent behaviour than historical behaviour. A sender with six months of excellent sending history followed by two months of silence has, from the provider's perspective, a two-month history of zero positive engagement. The historical data still exists but its weighting has decayed.

Best Practices

• Maintain a minimum sending cadence — even one campaign per month — to prevent reputation from fully resetting
• If a sending gap is unavoidable, warm up by sending to your most engaged subscribers first when resuming
• Monitor reputation scores through Google Postmaster Tools and Microsoft SNDS during the resumption period
• Expect temporarily reduced inbox placement for the first few campaigns after a gap and plan accordingly