How do mailbox providers build sender profiles?

Mailbox providers construct sender profiles by aggregating data across millions of messages over time. They watch how your domain and IPs behave and how recipients respond to your mail.

The profile includes authentication consistency (does SPF, DKIM, and DMARC pass reliably?), engagement patterns (do recipients open, click, reply, or delete without reading?), complaint rates (how often recipients hit the spam button), and bounce rates (are you sending to invalid addresses?).

Providers also track sending volume patterns. Sudden spikes or irregular schedules raise flags. They note whether your content triggers their spam filters and whether your links point to suspicious destinations.

Think of this as the harbor authority's dossier on every vessel that enters the port. Each voyage adds another entry. Consistent, clean arrivals build trust. Erratic behavior or contaminated cargo gets noted and remembered.