Reputation block at Gmail
Needs reviewdiag_441 · SendGrid · opened 14 min ago · cluster of 1,204 events
◈ Model reasoning
At 09:24 UTC, Gmail MX servers began rejecting SendGrid traffic with 550 5.7.1 ("unusual rate of unsolicited mail"). Rejection share climbed from 0.3% to 41% within 12 minutes across 1,204 messages.
This morning's newsletter batch to news.acme.com included a purchased list segment (import imp_2291) with a 9.8% unknown-user rate — 16× baseline. Gmail appears to have throttled the sending IPs in response. This matches the signature of a reputation block, not a content filter.
Fail over rules mail.acme.com and news.acme.com to AWS SES (healthy, 99.4% delivered), suppress the 118 addresses that hard-bounced, and quarantine import imp_2291 from future batches. SendGrid circuit is already open — approval makes the failover explicit and starts IP warming guidance.
Sample evidence events
All 1,204 events →| Message | Recipient MX | SMTP reply | Time |
|---|---|---|---|
| msg_9f2c81 | gmail-smtp-in.l.google.com | 550 5.7.1 | 09:38:14 |
| msg_66b2a1 | gmail-smtp-in.l.google.com | 550 5.7.1 | 09:37:48 |
| msg_51c9d7 | gmail-smtp-in.l.google.com | 421 4.7.0 | 09:36:55 |