A spam filter is a program that scans incoming emails and blocks suspicious ones from reaching the inbox. It checks for spam words, sender reputation, formatting issues, and more to determine if a message looks untrustworthy.
How spam filters work
Content: Looks for spammy language or weird formatting
Sender info: Flags emails from suspicious domains or IP addresses
Engagement history: Tracks if recipients open, delete, or mark your emails as spam
Why it matters
If your email trips a spam filter, your message might never be seen. Avoiding spam triggers and maintaining a clean sender reputation helps keep your messages where they belong—in the inbox.
Want to avoid spam filters? Have a look at our 24 tips on how to stay out of the spam folder.
