What are best practices for maintaining IP reputation?

IP reputation isn't a thing you fix once and forget. Mailbox providers are constantly re-evaluating based on what they see from your IP, which means every send either builds it up or chips it away.

Only send to people who asked. This sounds obvious but it's the foundation. No purchased lists, no scraped addresses, no 'they gave us their email somewhere' assumptions. Every address on your list should have explicitly opted in. This is where most reputation problems start.

Keep complaint rates below 0.1%. When someone hits 'Report Spam', that signal goes straight to the mailbox provider's reputation calculation for your IP. Set up feedback loop notifications from Yahoo and Microsoft so you can suppress complainers the moment they flag you. Gmail doesn't have a traditional feedback loop, but you can monitor your spam rate in Google Postmaster Tools.

Process bounces immediately. Hard bounces come off the list at once. Soft bounces get monitored: if an address consistently fails, suppress it. Sending repeatedly to dead addresses is one of the clearest signals that you're not managing your list.

Authenticate properly. SPF, DKIM, and DMARC all need to be set up correctly, with alignment passing, not just the individual checks. Authentication isn't directly a reputation signal, but failing it makes everything else worse.

Keep volume consistent. Sudden spikes raise flags. Long quiet periods mean you'll face re-scrutiny when you start sending again (similar to a cold IP). Predictable patterns build trust.

Separate your mail streams. Transactional email (receipts, password resets) should go out on different IPs than marketing. If a campaign tanks your reputation, your transactional mail stays clean.

Reputation is built slowly and can drop fast. Check IP reputation recovery if you're already dealing with damage.