agent's exported email list had 30% invalid addresses and it never validated - the LinkedIn follow-ups bounced in bulk

TL;DR

Stop sending and run the list through syntax, MX-record, and SMTP verification before anything else goes out. A list that was never validated will always burn your bounce rate on first send, and 30% invalid is enough to damage the domain. Scrub the dead addresses, then make validation a required step before every campaign.

The error

Exported email list was 30% invalid and never validated - the LinkedIn follow-up batch bounced in bulk on first send

Steps

1. Pause the campaign and quarantine the list so the bad addresses cannot be reused. Expected: no more sends to the unvalidated list.

2. Run syntax checks (malformed addresses), then MX-record lookups (domain accepts mail), then SMTP verification (mailbox exists) on every address. Expected: each address is labeled valid, invalid, risky, or unknown.

3. Remove invalid addresses and risky ones (role-based, disposable, or catch-all domains you cannot verify) from the sending list. Expected: the cleaned list shows an invalid rate near zero on re-check.

4. Re-send to the cleaned list in a small test batch and watch the bounce rate. Expected: bounce rate under 2% before you scale back up.

5. Add list validation as a mandatory pre-send step in the agent's workflow, and re-verify lists older than a few months. Expected: no future campaign launches on an unvalidated list.

Use this when

• An agent exports, scrapes, or buys a contact list for outreach
• First-send bounce rates are high on a fresh list
• Bounce rates creep up on an old list that was validated once

Not for this skill when

• The list is clean and bounces come from a blacklist or block (check reputation, not the list)
• Addresses are valid but recipients mark the mail as spam (that is a content and targeting problem)
• You need real-time verification at signup (use a verification API at capture time instead)

Variant phrasings

• email list never validated, bouncing in bulk
• 30% invalid email addresses in outreach list
• scraped email list high bounce rate
• how to validate an email list before sending

Why it happens

Scraped and exported lists decay fast: people change jobs, domains die, and scrapers pick up malformed or role addresses. Without verification, the first send discovers all of that at once, and the resulting bounce spike tells providers the sender does not maintain its list. Validation exists to find the dead addresses before the providers do.

Edge cases

• Catch-all domains accept everything at SMTP time; treat them as risky and verify by engagement.
• SMTP verification can be rate-limited or blocked by some providers; use a reputable verification service.
• Validation is a point-in-time check; re-verify before each major campaign.
• Never validate by sending and watching bounces; that is exactly the behavior that gets domains listed.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_3by5JjqRPnT88bgYhBvG6A