Verify a Substack or beehiiv Export Before Migrating: A Column-by-Column Walk-Through
To verify a Substack or beehiiv export, download the subscriber CSV, run the email column through a bulk verifier and import the valid rows, keeping paid subscribers and any risky rows you choose to keep. A migration starts a fresh sending history on the new platform, so it is the best moment to leave bad addresses behind. The email verification for newsletter creators page covers the check; the Substack export guide and beehiiv export guide show where the CSV is.
Step 1: read the columns
A subscriber export usually has email, signup date, subscription status and paid status. Keep all of them. Verification works on the email column, and the rest tells you who to protect. The CSV column editor pulls out only what you need.
Step 2: verify the email column
Upload the CSV on the verify page. Each row comes back valid, risky or invalid with a reason.
Step 3: decide per reason
| Reason | Free subscriber | Paid subscriber |
|---|---|---|
| Mailbox not found, No mail server | Leave behind | Contact by other means |
| Typo domain | Fix, re-check | Fix, re-check |
| Disposable address | Leave behind | Review by hand |
| Accepts all addresses, Role address | Import, send in a small batch | Import |
| Valid | Import | Import |
Step 4: import into the new platform
Import the cleaned file, then send a warm-up issue to engaged rows first. The guide to moving a list to beehiiv, Kit or Substack covers the import steps and the Kit to Systeme.io migration shows another route.
Step 5: keep the old suppression list
Bring across unsubscribes and bounces from the old platform. Re-importing someone who unsubscribed is a worse mistake than a bad address. The suppression list merger combines the files.
What this cannot do
- It does not judge engagement; use opens and clicks for that.
- Yahoo and AOL accept mail for any address during the check, and Microsoft consumer mailboxes are not probed, so they come back risky.
- A valid result is a snapshot. A mailbox can close after the check.
Check before you move
Upload your export on the verify page: the first 100 checks are free with a Google sign-in, no card. For bigger lists, see list cleaning and pricing.
Common questions
How do I verify a Substack export before migrating?
Download the subscriber CSV, take the email column, run it through a bulk verifier and import only the valid rows, plus any risky rows you choose to keep.
Do I lose paid subscribers if I filter?
Do not remove paid subscribers on a risky result alone. Check them separately and contact paid rows with a problem another way.
Why clean before a move?
A new platform starts your sender reputation fresh. Importing bad addresses puts bounces on the first sends.
Should I keep unengaged subscribers?
That is an engagement question, not an address question. Verification only removes addresses that cannot receive mail.
What does it cost?
The first 100 checks are free with a Google sign-in, no card. Pro is $39 a month, with the first 100,000 checks a month at full speed, then slower, never cut off.
Check your list before you send
Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.