Sender reputation (email)
What is Sender reputation (email)?
Sender reputation is a mailbox provider's ongoing trust score for a sending domain or IP address, calculated from signals like spam complaint rate, bounce rate, engagement (opens and clicks), and authentication pass rates (SPF, DKIM, DMARC) — and it directly determines whether future messages land in the inbox, the spam folder, or get blocked outright. Unlike a one-time compliance check, sender reputation is continuously recalculated, so a sudden spike in complaints or bounces can degrade inbox placement even for a previously well-established sender.
More detail
Warming up a new sending domain or IP gradually — starting with low volume to engaged recipients before scaling up — is a standard practice to build reputation, since mailbox providers treat a sudden high-volume burst from a brand-new sender as suspicious.
Because reputation is continuously recalculated, a single bad campaign with high complaint or bounce rates can measurably hurt deliverability for subsequent, otherwise well-targeted sends from the same domain.
Frequently asked
- What signals go into a sender's email reputation score?
- Mailbox providers weigh spam complaint rate, bounce rate, recipient engagement (opens and clicks), and how consistently the domain passes SPF, DKIM, and DMARC authentication — combined into an ongoing trust signal rather than a single fixed rating.
- Why do new sending domains need to 'warm up' gradually?
- A brand-new domain or IP suddenly sending high volume looks suspicious to mailbox providers, so gradually ramping up volume to engaged recipients first is the standard way to build a positive reputation before scaling to full send volume.
See also
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