How does engagement factor into spam detection?

You've probably noticed that some senders land in your inbox every time, even if their emails are promotional, while others hit spam after just a few messages. That's engagement filtering at work. Mailbox providers like Gmail, Outlook, and Yahoo Mail don't just look at your technical setup. They watch how real people actually behave when your emails arrive.

The signals they track include opens, clicks, replies, saves, moves to inbox, and spam reports. Each one is a vote. Opens and clicks say "keep this coming." A spam report says "this person doesn't want this." Deleting without opening, over and over, quietly says the same thing. Filters aggregate these signals across millions of recipients to build a picture of whether your emails are wanted or not.

Here's where it gets personal. Gmail in particular uses machine learning to tailor filtering to each individual inbox. An email from a cycling brand might go straight to inbox for someone who clicks every newsletter they send, and straight to spam for someone who's never touched one. Same sender, same message, different outcome based on personal history. That's why your open rate is an average. Some of your subscribers are actively helping your deliverability and some are quietly hurting it.

For senders, a few practical benchmarks to keep in mind. Open rates below 10% on a consistent basis are a warning sign. Spam complaint rates above 0.3% will get you noticed by Gmail's Postmaster Tools and can trigger filtering. Outlook tends to be less transparent but is equally sensitive to complaint volume. And if a large chunk of your list hasn't opened anything in 6 to 12 months, those subscribers are likely dragging down your reputation even if they haven't complained. (Silence isn't neutral. It reads as disinterest.)

The fix isn't to send more or change your subject lines. It's to send to people who actually want what you're sending. Segment out disengaged subscribers before they damage your reputation with the engaged ones. A legitimate sender can still end up in spam if they ignore these signals long enough.

If your list feels stale, we clean them at RME (hi ;). Or if you want to dig into your current setup first, our SOS hotline is free and we'll tell you honestly what we see.