What is sender reputation?

Sender reputation is how mailbox providers decide whether your emails belong in the inbox or the spam folder. It's a score based on your past behavior, tracked at both the domain level (what you send from) and IP level (where it comes from).

Think of it like credit, but for email. Good history gets you into inboxes. Bad history gets you filtered, throttled, or blocked entirely. Gmail, Outlook, and Yahoo each track your reputation independently, so you can have great reputation with Gmail and terrible reputation with Outlook at the same time.

What shapes your reputation:

• List quality. If you're hitting a bunch of bad addresses, spam traps, or old contacts who never open, that's a red flag.
• Engagement. Opens and clicks signal that people want your email. No engagement signals the opposite.
• Spam complaints. Every time someone marks your email as spam, your reputation takes a hit. Keep this below 0.1% if you can.
• Bounce rate. High bounces tell mailbox providers you don't know who you're sending to. That's spammer behavior.
• Sending consistency. Spiking from 1,000 emails a day to 50,000 overnight looks suspicious. Ramp up slowly.
• Authentication. Having SPF, DKIM, and DMARC set up correctly proves you're a legitimate sender.

Here's the frustrating part: you can't see your exact reputation score. Mailbox providers don't publish it. What you CAN see are the symptoms (inbox rate dropping, emails getting deferred, bounce messages mentioning reputation). You can also check external signals like blocklist status and domain reputation tools, but those are proxies, not the real score.

Two types of reputation matter: IP reputation (tied to the mail server sending your email) and domain reputation (tied to your From domain). Most ESPs use shared IPs, which means your IP reputation is shared with other senders on that server. Your domain reputation is yours alone. Over time, domain reputation has become MORE important than IP reputation because it's harder to fake.

If you're just starting out, you don't have any reputation yet. That's called a warmup period. Mailbox providers will watch you closely at first, so start small, send only to engaged contacts, and prove you're trustworthy before ramping up volume.

Want to check where you stand? Run your domain through our free blocklist checker to see if you're flagged anywhere. If you're seeing inbox rate problems and don't know why, hit up our SOS hotline and we'll help you figure out what's broken.