Sender reputation
In short
Sender reputation is how mailbox providers rate the trustworthiness of the domain and IP address you send email from. A good reputation helps your messages reach the inbox. A poor one pushes them to spam or blocks them.
Providers do not publish one score. They judge your behavior over time, including how recipients react and how clean your sending practices are. For outbound teams, protecting reputation protects every future campaign.
What affects sender reputation
- Spam complaints: recipients marking your email as spam.
- Bounce rate: sending to invalid addresses signals poor list quality.
- Engagement: opens, replies, and deletions without reading.
- Authentication: SPF, DKIM, and DMARC set up correctly.
- Sending patterns: sudden jumps in volume look suspicious.
- Spam traps: old or scraped addresses that flag careless list building.
How to protect it
Verify addresses before sending
Remove invalid and risky addresses to keep bounces low.
Authenticate your domain
Set up SPF, DKIM, and DMARC.
Warm up new domains
Raise volume gradually. See domain warmup.
Send relevant messages
Targeted outreach earns replies and fewer complaints.
Make opting out easy
A clear opt-out reduces spam complaints.
Use a separate domain for outbound
Keep cold outreach away from your main company domain.
Example
Say a team sends 500 emails a day from a new domain on day one, using an unverified list. Bounces spike and a few recipients report spam. Messages start landing in spam. A better path is to verify the list, start at a small daily volume, and grow it slowly while watching bounces and replies.
How to monitor it
Watch bounce rate, spam complaint rate, and reply rate by domain. Mailbox provider postmaster tools and inbox placement tests show how your mail is treated. Pause sending on any domain whose numbers worsen.
Common mistakes
- Scaling volume before the domain is warmed up.
- Buying or scraping lists without verification.
- Ignoring complaints until placement collapses.
- Sending from the main company domain.
Sender reputation FAQs
What is sender reputation?
Sender reputation is the level of trust mailbox providers assign to your sending domain and IP address, based on your past behavior. It influences whether your emails land in the inbox, go to spam, or are blocked entirely.
How do you improve sender reputation?
Verify addresses before sending, set up SPF, DKIM, and DMARC, warm up new domains gradually, send relevant messages, and make opting out easy. Keep bounce and spam complaint rates low, and pause sending if either starts rising.
What damages sender reputation?
High bounce rates, spam complaints, sending to spam traps, sudden spikes in volume, weak authentication, and low engagement all damage reputation. Sending irrelevant messages to unverified lists is the most common cause for outbound teams.
How long does it take to recover sender reputation?
It varies. Recovery usually takes weeks of consistent, low-volume, high-quality sending with clean lists. A badly damaged domain may be easier to replace than repair, so many teams isolate outbound on separate domains.
