follow-up agent got the sending domain blacklisted - bounce rate hit 12% and the agent kept retrying hard bounces

TL;DR

Stop all retries immediately, permanently suppress every hard bounce, and check whether the domain or IP is on a public blacklist before sending anything else. Retrying a hard bounce is never useful: the address is dead, and every retry just adds to the bounce rate that gets you listed. Request delisting only after the cause is fixed, then re-warm slowly.

The error

Sending domain blacklisted - bounce rate hit 12% because the agent retried hard bounces instead of suppressing them

Steps

1. Halt all sending and disable the retry loop on the outreach agent. Expected: no new mail leaves the domain while you remediate.

2. Export the bounce log and separate hard bounces (address does not exist, blocked) from soft bounces (mailbox full, temporary failure). Expected: a clear list of dead addresses versus temporarily failing ones.

3. Add every hard bounce to the suppression list permanently; cap soft-bounce retries at 3 attempts with backoff, then suppress. Expected: the active list contains zero known-bad addresses.

4. Check the domain and sending IP against public blacklist checkers. Expected: you know exactly which lists flag you, if any.

5. If listed, fix the cause first, then submit a delisting request to each list with a short explanation of what changed. Expected: the delisting request is accepted because the retry behavior is fixed.

6. Re-warm with a small, engaged, recently-verified segment before resuming normal volume. Expected: bounce rate stays under 2% and placement recovers.

Use this when

• Bounce rate spikes and deliverability collapses in the same window
• An agent retries failed sends without distinguishing hard from soft bounces
• The domain or IP appears on a blacklist after a campaign

Not for this skill when

• Bounces are all soft and transient (that is a throttling or warmup issue, not a blacklist issue)
• A single receiving domain rejects you (check that domain's postmaster guidance instead)
• You were listed for content reasons with a clean list (then the template is the problem)

Variant phrasings

• domain blacklisted after high bounce rate
• agent kept retrying hard bounces and got us listed
• 12% bounce rate, sending domain blocked
• how to get off an email blacklist after a bad campaign

Why it happens

Mailbox providers track bounce rates per sender; sustained rates far above roughly 5% signal a bad list or a broken sender, and blacklists pick that up fast. A hard bounce means the address will never accept mail, so retrying it converts one dead address into many bounces. The agent treated every failure as transient and kept hammering dead addresses until the rate crossed listing thresholds.

Edge cases

• Catch-all domains accept-then-bounce, which inflates hard bounces; verify before sending.
• List age matters: old lists decay fast, so re-verify any list older than 6 months.
• Shared IPs: if the IP is burned by another tenant, delisting your domain alone may not fix placement.
• Add a bounce-rate alert (e.g. over 5% in an hour) so the loop stops itself next time.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_GfhvK-LnvOMfAqnTuT8PCg