A deliverability warning means a sending-reputation metric crossed a risk threshold — rising bounces, spam complaints, or a spam-trap hit. It's an early signal to slow down and fix the cause before your domain reputation takes real damage.
What triggered it
The warning names the metric: bounce rate, complaint rate, spam-trap hit, or authentication problem. Each points at a different root cause — bounces mean list quality, complaints mean targeting or copy, traps mean stale or purchased data.
Common causes
Sending to unverified or stale addresses (bounces), messaging that annoys recipients (complaints), old lists containing spam traps, or ramping volume faster than the mailbox warmed for. Broken SPF/DKIM/DMARC can trigger it too.
Fixes
Slow sending immediately — don't push through a warning. Tighten enrichment and email verification to cut bounces. Review targeting and copy if complaints are the driver. Re-check authentication. Let the mailbox recover with clean, paced sending (see Mailbox health badges explained).
Why it matters
Domain reputation is slow to build and fast to lose. A warning is turgo protecting you — heed it early and recovery is quick; ignore it and you risk landing in spam folders across the board.
