What factors influence IP reputation?

Your IP address has a history. Every time mail leaves it, receiving servers take note. Over time, that history becomes a score that determines how quickly your emails clear the gates at Gmail, Outlook, and everywhere else. So what goes into that score?

Here are the main factors mailbox providers and spam filters use to judge your IP.

Complaint rate. When recipients hit "this is spam", that's a vote against your IP. A complaint rate above 0.1% at Gmail starts causing real problems. Above 0.3% and you're in serious trouble. This is the single factor that tanks reputations fastest.

Bounce rate. High bounce rates, especially hard bounces, tell receiving servers your list is messy. A messy list means you're either buying addresses, letting signups go stale, or skipping validation. Any of those is a red flag.

Spam trap hits. Spam traps are addresses that should never receive mail from a legitimate sender. If your IP hits them, it signals poor list hygiene or, worse, a purchased list. Even one hit can trigger a blocklist entry.

Volume consistency. Sending 10 emails one day and 100,000 the next looks suspicious. Spam operations tend to burst and disappear. Consistent, predictable volume builds trust. Sudden spikes erode it.

Blocklist appearances. Being listed on Spamhaus, Barracuda, or SpamCop directly affects delivery. Some receiving servers reject mail from listed IPs outright. Others apply extra scrutiny. Either way, it hurts.

Authentication signals. An IP consistently sending authenticated mail (SPF passing, DKIM signing, DMARC aligned) builds more trust over time than one that fails or sends unsigned. Authentication alone won't save bad behavior, but it's part of the picture.

One thing worth knowing: if you're on a shared IP, you inherit the history of every sender on that address. Your sending can be perfectly clean and still suffer if a neighbor is sending garbage. That's not a reason to panic about shared IPs, but it's a reason to understand what you're working with.

Want a quick check on where your IP currently stands? Run it through our free Blocklist Checker to see if you've picked up any flags. If you're seeing delivery problems and can't pinpoint why, our SOS hotline is free and we'll actually help you dig in.