How do engagement rates differ across ISPs?

Each major mailbox provider calculates and weights engagement signals differently based on their filtering philosophy and user base characteristics.

Gmail heavily emphasizes user engagement signals. Opens, clicks, and especially replies significantly influence filtering decisions. Their machine learning systems continuously adapt based on user behavior.

Microsoft gives more weight to IP reputation and blocklist data alongside engagement. Their SmartScreen filter blends multiple signal types.

Yahoo closely watches complaint rates through their Complaint Feedback Loop. High spam complaints quickly damage Yahoo deliverability.

Different ISPs are like different port authorities with their own inspection priorities. Some care most about cargo quality, others about the ship's history, others about merchant complaints. Successful senders satisfy all of them.