You are about to send a campaign. Your list is sitting in your ESP. Some of those addresses will bounce. You do not know which ones. You could find out in the next 60 minutes before a single email goes out, or you could let the campaign run and find out afterward, when the bounces have already registered as negative signals against your sending domain.
This checklist gets your list clean before you send. It takes 60 minutes. It prevents the reputation damage that takes weeks to recover from.
The 60-Minute Pre-Send List Cleaning Checklist
Minutes 1-2: Decide which segments need cleaning
Not all campaigns carry equal risk. Apply the full cleaning workflow to any campaign where one or more of these is true:
☐ The send audience includes contacts not emailed in the past 60 days
☐ The send audience includes contacts from any external import in the past 6 months
☐ Your last full list verification was more than 90 days ago (B2B) or 180 days ago (consumer)
☐ Your most recent campaign's hard bounce rate exceeded 0.3%
☐ This is a high-stakes campaign (product launch, seasonal, fundraising)
If none of these apply, you send weekly to a recently verified, actively engaged subscriber list, your abbreviated pre-send check (Postmaster Tools domain reputation + recent bounce rate) may be sufficient.
If any of these apply, continue through the full checklist.
Minutes 2-12: Export your campaign audience
Export the contacts in your planned campaign audience as a CSV. Include email address plus any source or date fields that help you analyse results later.
Minutes 12-15: Upload to BounceProof
Go to bounceproof.co. Upload the CSV to bulk verification. Click Start. Processing begins immediately. You will receive an email when results are ready.
Minutes 15-30: Check Postmaster Tools while you wait
Log into Google Postmaster Tools (postmaster.google.com). Check three things:
Domain reputation still High? If not, investigate before sending.
Spam rate still below 0.08%? If not, check which recent campaign drove it up.
Authentication pass rates still above 95% for SPF and DKIM?
If any check fails, resolve it before the campaign deploys regardless of what the verification results show.
Minutes 30-45: Results arrive — act on each classification
When BounceProof emails your results, download the file. Apply these actions immediately:
Invalid addresses:
Export to a suppression file. Upload to your ESP's suppression list. The invalid contacts are now excluded from this and all future campaigns.
Update your CRM: mark these contacts' email status as "Invalid" with today's date. Prevents reactivation from future imports.
Disposable addresses:
Suppress permanently. Investigate which form or source produced them; high disposable rates indicate a specific capture point worth fixing.
Catch-all addresses:
Make a decision based on your current Postmaster Tools domain reputation:
High reputation: include catch-all contacts but monitor their bounce rate separately
Medium or below: exclude catch-all from this campaign
Unknown addresses:
If time allows, mark these for 48-hour re-verification and exclude them from this campaign. If the campaign cannot wait, include verified-valid addresses only and re-verify unknowns for the next campaign.
Role-based addresses:
Exclude from this promotional campaign. They may be retained for relevant transactional communications.
Minutes 45-55: Rebuild your campaign audience from verified results
Import your verified-valid contacts back to your ESP. Configure your campaign to send to this verified segment only,y not the original unfiltered audience.
If your ESP requires rebuilding the campaign audience after the import, this is the step where that happens. Confirm the audience count reflects the suppression you just applied.
Minutes 55-60: Final send checks
Before deploying:
☐ Hard bounce rate from most recent 3 campaigns: below 0.5%?
☐ Domain reputation in Postmaster Tools: High?
☐ Campaign audience reflects post-verification suppression?
☐ Unsubscribe link visible and working in email preview?
☐ List-Unsubscribe-Post header present in email headers?
All five checked? Deploy with confidence.
What This 60 Minutes Prevents
This workflow is a 60-minute investment. Here is what it prevents.
Prevented: Hard bounce spike. Without cleaning, every invalid address in your audience generates a hard bounce. At a 10% invalid rate on a 20,000-contact campaign, that is 2,000 hard bounces and a 10% bounce rate, far above the 0.5% threshold that triggers reputation damage.
Prevented: Domain reputation decline. Those 2,000 bounces register against your sending domain in Gmail's reputation model. Domain reputation moves from High to Medium. Inbox placement drops. Open rates decline for the next 4 to 8 weeks.
Prevented: ESP compliance notification. Mailchimp, Klaviyo, Brevo, and other ESPs monitor account-level bounce rates. Sustained high bounce rates trigger compliance notifications and potential account review. Pre-send verification keeps bounce rates below the threshold that triggers these notifications.
Prevented: Reputation recovery cost. The alternative to 60 minutes of prevention is 6 to 10 weeks of reputation recovery, reduced sending volume, limited campaign audiences, and restricted access to your full list.
When You Need Less Than 60 Minutes
For routine weekly sends to a recently verified, consistently engaged subscriber list, the full 60-minute workflow is overkill. Use this abbreviated 10-minute version:
☐ Check Postmaster Tools: domain reputation still High? Spam rate still below 0.08%?
☐ Check most recent campaign bounce rate: still below 0.3%?
☐ Confirm list was verified within the past 90 days (B2B) or 180 days (consumer)
If all three are green, proceed. No additional verification needed for this send.
If any is not green, run the full 60-minute workflow before this campaign deploys.
Building This Into Your Standard Workflow
The 60-minute checklist works best when it is built into your campaign planning process, not added as a last-minute step.
When a campaign is scheduled in your project management tool or campaign calendar, add these tasks:
Campaign audience export: 2 days before send date
BounceProof verification: 2 days before send date (linked to export task)
Suppression import: 1 day before send date
Pre-send final check: day of send
This scheduling gives you time to act on results without rushing. If verification reveals a significant quality problem, you have a day to investigate the source rather than making hasty decisions under send deadline pressure.
Frequently Asked Questions
Do I need to verify my list before every campaign?
Not always. Verify quarterly and before campaigns targeting older, imported, or high-risk segments.
Can I clean a list the day before a campaign?
Yes. Smaller lists can typically be verified and suppressed before the next-day campaign.
How long does large-list verification take?
Processing time depends on list size and provider capacity. Large lists should be uploaded well before the campaign.
Should I verify recently engaged contacts again?
Usually not if they were verified recently and remain actively engaged.
When should I reverify an old email list?
Reverify lists that have not been emailed for 60+ days or have been stored for an extended period.
Conclusion
Every campaign has a 60-minute window before the send button where you can prevent the bounce damage that would otherwise take weeks to repair. The investment is 60 minutes and the cost of verification credits. The alternative is hours of diagnosis and weeks of restricted sending.
Upload your campaign audience now. BounceProof returns results within 30 to 90 minutes for most list sizes.
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