What is sender reputation?
Sender reputation is the trust score that inbox providers assign to your sending domain and IP based on your sending history — bounce rates, spam complaints, engagement, and authentication — and it directly determines whether your mail reaches the inbox.
Inbox providers can't read your mind, so they judge you by your record. Sender reputation is the running tally they keep: how often your mail bounces, how often recipients mark it as spam, how often they open and reply, and whether your domain is properly authenticated. A strong reputation buys you the inbox; a weak one buys you the spam folder.
Reputation is built slowly and lost quickly. A single campaign to a dirty list — high bounces, a spike in complaints — can undo months of careful sending. That asymmetry is why list hygiene and verification aren't optional niceties; they're reputation insurance.
The levers are the familiar ones, working together. Keep bounce rates low by verifying before you send. Keep complaint rates under 0.3% by emailing people who expect to hear from you and making unsubscribe easy. Warm up new sending domains gradually. Authenticate with SPF, DKIM, and DMARC so providers can confirm the mail is really from you.
Reputation also has memory and geography: it attaches to both your domain and your sending IP, and damage in one mailbox provider's eyes doesn't automatically heal in another's. Protecting it is cheaper than rebuilding it, which is the whole argument for verifying lists at the moment of send.
Frequently asked questions
How do I improve my sender reputation?
Verify lists before sending to keep bounces low, hold complaints under 0.3%, warm up new domains gradually, authenticate with SPF/DKIM/DMARC, and email people who expect your mail. Consistency over time is what rebuilds trust.
How long does it take to recover a damaged reputation?
Weeks to months of clean, low-bounce, low-complaint sending. Reputation is lost quickly and rebuilt slowly, which is why preventing damage through verification is far cheaper than recovering from it.