Level: Beginner
Spam filtering evaluates a combination of authentication, reputation, content, and engagement signals, not any single factor in isolation.
Authentication Results Feed Directly Into Filtering
A message failing SPF, DKIM, or DMARC checks is treated with significantly more suspicion by filtering systems than a properly authenticated one, often regardless of content quality.
Reputation Signals Carry Significant Weight
The sending IP and domain's historical behavior — complaint rates, bounce rates, prior spam reports — heavily influences how new messages from that source are treated.
Content and Engagement Signals Round Out the Picture
Message structure, link patterns, and how recipients have historically engaged with mail from this sender all factor into the final filtering decision.
Next step: Use the Blacklist Lookup to check whether your sending domain or IP currently appears on any blocklists that spam filters commonly reference.