SendGrid suppression lists silently blocking sends

Symptom: 202 accepted, then dropped events citing a suppression reason, for addresses you believe are fine.

Cause candidates:

1. Bounce list: the address hard-bounced before. Correct behavior.
2. Unsubscribe list: the recipient opted out, possibly via a different product surface.
3. Spam report list: the recipient reported spam; also correct behavior.
4. Stale sync: your CRM re-adds suppressed addresses every night.

Confirmation: check Suppressions in the console for the address and the list it sits on.

Fix:

1. For genuinely fixed addresses (typo corrected, re-opted-in with proof), remove from the specific list and resend once.
2. Fix the sync so suppressed addresses are never re-imported as mailable.
3. Never bulk-clear suppression lists to improve 'deliverability'. It does the opposite.

Verification: the address sends normally after targeted removal, and the sync stops re-adding suppressed addresses.

The bounces doc: bounced addresses land on the bounce suppression list and repeat sends are suppressed. The event reference: dropped 'Bounced Address' and 'Unsubscribed Address' reasons. Suppressions exist to protect reputation; bulk-clearing them recreates the problem. Sources: https://docs.sendgrid.com/ui/sending-email/bounces | https://docs.sendgrid.com/for-developers/tracking-events/event