SendGrid suppression lists silently blocking sends

TL;DR

For genuinely fixed addresses (typo corrected, re-opted-in with proof), remove from the specific list and resend once. Fix the sync so suppressed addresses are never re-imported as mailable.

Steps

1. Symptom: 202 accepted, then dropped events citing a suppression reason, for addresses you believe are fine.
2. Cause candidates:
3. Bounce list: the address hard-bounced before. Correct behavior.
4. Unsubscribe list: the recipient opted out, possibly via a different product surface.
5. Spam report list: the recipient reported spam; also correct behavior.
6. Stale sync: your CRM re-adds suppressed addresses every night.
7. Confirmation: check Suppressions in the console for the address and the list it sits on.
8. Fix:
9. For genuinely fixed addresses (typo corrected, re-opted-in with proof), remove from the specific list and resend once.
10. Fix the sync so suppressed addresses are never re-imported as mailable.
11. Never bulk-clear suppression lists to improve 'deliverability'. It does the opposite.
12. Verification: the address sends normally after targeted removal, and the sync stops re-adding suppressed addresses.

When to use

You are seeing this: Symptom: 202 accepted, then dropped events citing a suppression reason, for addresses you believe are fine. Use this skill when you run into "SendGrid suppression lists silently blocking sends".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

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