Verify every list right before it sends

What it does

Bounces are the fastest way to burn a sending domain. They come from old lists, bad data and bad uploads, and they tend to arrive all at once. Most of it is preventable with a few habits: verify right before you send, test every batch small, set your own stop line, and watch the first hour after anything starts.

What you need

• Your list, and the date each contact was pulled
• An email verifier. Most sending tools have one built in
• Your sending tool’s bounce numbers

How it works

1. 1

   Verify on the day you send

   People change jobs every month, so a list verified in March is decaying by May. Verify right before the list goes into a campaign, not the day you pulled it, and treat anything pulled months ago as higher risk.

2. 2

   Drop invalid and risky, and don’t trust “valid”

   Remove everything marked invalid or risky. Then remember that “valid” means the mail server answered, not that a person reads that inbox. In one of my campaigns, about half the addresses that bounced had come back valid.

3. 3

   Send a small sample from each batch first

   Lists arrive in batches: one export, one upload, one source. A verifier can’t spot a bad batch. Send 20 to 50 from each batch, wait a day, and check the bounces before the rest goes out.

4. 4

   Set your own stop line

   Some sending tools only pause a campaign on their own above 5% bounces. Set a lower line, like 3%, and check it yourself.

   Google Sheets: paste into A1

   Sent	400
   Bounced	9
   Bounce rate	=B2/B1
   Stop?	=IF(B3>=3%,"Stop, and find the bad batch","Keep going")

5. 5

   Watch the first hour after any start or restart

   Some tools won’t pause a campaign again for days after you resume it. Check bounces within the first hour of any start or restart, then again before the day ends.

6. 6

   Block anyone who bounced or asked to stop

   Add them to your workspace blocklist, not just the campaign, so no inbox can reach them again. Re-verifying can reset a contact’s status in some tools, so check that bounced and replied contacts are still marked after any re-check.

What good looks like

Bounces stay under 2% on every campaign, every batch was tested small before it went out, and nobody who bounced or opted out gets a second email.

Mistakes to skip

• Verifying once, months before sending.
• Treating “valid” as safe.
• Restarting a paused campaign and not looking at it for a day.