Sender reputation
A composite score mailbox providers maintain for every sending IP and domain — your invisible deliverability grade.
Every IP address and domain that sends email accumulates a reputation score at every mailbox provider (Gmail, Outlook, Yahoo, etc.). This score determines whether your email lands in the inbox, the promotions tab, the spam folder, or gets blocked outright.
Inputs to reputation: bounce rate, complaint rate, engagement rate (opens, replies, deletes-without-reading), authentication success (SPF/DKIM/DMARC), volume consistency, and sometimes content signals.
Reputation is per-mailbox-provider — Gmail's view of you can be excellent while Outlook flags you as spam. BoomSauce surfaces reputation per (domain × provider) on the /admin/reputation dashboard, sourced nightly from SendGrid Stats.