Sender reputation
Sender reputation is a receiving organisation's running opinion of your mail, kept against your sending domain and the address you send from. It is built from how often your messages bounce, how often readers complain, how they engage, and whether your mail authenticates. Nobody publishes the formula, every provider keeps its own, and it changes with every campaign you send.
At a glance
- Category
- Deliverability
- Kept per
- Mailbox provider — there is no single global score
- Attached to
- The sending domain, and the sending address
- Built from
- Bounces, complaints, engagement, authentication, volume pattern
- Visible through
- Provider postmaster tools, partially
- Changes
- Continuously, with a memory of weeks rather than days
How it works
Each receiving organisation records what happens to the mail it accepts from you and folds it into a rolling view. Messages to addresses that do not exist count against you, as do complaints, and both are weighted heavily because they indicate a list you do not control. Engagement counts in your favour: opens where they can be measured, replies, messages moved out of junk. Authentication is the entry condition, and an abrupt change in volume is itself a signal, independent of content.
Why it matters
Reputation is the variable that decides placement, and it is cumulative, so it cannot be fixed on the day you need it. That asymmetry is the thing to internalise: it is built slowly by sending wanted mail to people who asked, and it can be spent in a single afternoon by mailing a list nobody has touched in two years. It also attaches mostly to the domain, which is why marketing and transactional mail are usually kept on separate subdomains.
Example
A team keeps its complaint rate low for a year and its mail lands reliably. They then import a conference attendee list and send it a product announcement. Bounces and complaints spike, and within days mail from the same domain — including password resets — starts arriving in junk at two providers. They stop mailing the imported list, keep sending to the engaged audience, and placement recovers over several weeks.
Common mistakes
- 01Trying to repair reputation by sending more, which gives the provider more of the evidence that caused the problem.
- 02Sharing one domain between bulk campaigns and password resets, so a bad campaign takes the critical mail with it.
- 03Assuming a new provider resets your reputation, when the domain and the list travel with you.
- 04Watching only the last few days, when the view a provider keeps has a memory measured in weeks.
Related terms
Frequently asked questions
Can I see my sender reputation?
Only partially. Some large providers offer postmaster tools that show a coarse view of your domain's standing with them, and there is no cross-provider score to look up.
Is reputation attached to the domain or the IP address?
Both, with the domain mattering more for most senders today. That is why moving to a new sending address rarely fixes a problem caused by list quality.
How long does a bad campaign affect me?
Typically weeks, because the view is a rolling one. Reducing volume to your most engaged recipients is what shortens it; continuing at full volume lengthens it.
Sources
Last updated 16 September 2026.
Start sending this morning
Verify a domain and send your first email in minutes.