A file must be no larger than 100 MB and no larger than 1,000,000 email rows. Meeting one limit does not override the other.
Six-step large-list workflow
Prepare the source
Export a UTF-8 CSV or TXT file, keep the original untouched, and add a stable row ID if your source system does not already provide one.
Check both limits
Confirm the file is no larger than 100 MB and contains no more than 1,000,000 email rows. The stricter limit wins.
Split deterministically
For larger exports, create sequential chunks with a documented row range, source filename, export timestamp, and shared campaign or customer identifier.
Run local preflight
Map the email column, count duplicates and malformed rows, and review the maximum unique verification requirement before credits are reserved.
Verify and reconcile
Track each file ID independently, keep provider reasons visible, and join results back to the original rows using the stable row ID.
Archive responsibly
Store the assessment and final result together, apply suppression rules, and follow your retention and deletion schedule.
What to include in every chunk
A reconciliation key
Use a stable row ID or source-system identifier. Keep the original source filename, chunk number, inclusive row range, export timestamp, and customer or campaign identifier beside the chunk. This makes it possible to join results back to the source without relying on row order alone.
source=Q3-leads.csv · chunk=04-of-12 · rows=300001-400000 · export=2026-09-23 · key=CRM_ID
What large-file cleaning does not prove
Capacity is not deliverability
A file limit describes what the workflow can process. It does not establish consent, mailbox existence, inbox placement, or guaranteed delivery. Keep valid, invalid, and unknown evidence separate and apply suppression rules before sending.
Continue the workflow
Guide questions
What is the current Refresh List file limit?+
The current workflow supports files up to 100 MB and up to 1,000,000 email rows per file. A file must satisfy both limits.
Can I verify multiple large lists?+
Yes. Multiple lists can be uploaded and tracked independently from one workspace, subject to the limits and available credits for each file.
How should I split a file larger than the limit?+
Split it into deterministic chunks with stable row IDs, keep the original file unchanged, and record the chunk range and source filename. Do not split randomly without a reconciliation key.
Do duplicate rows count toward the bill?+
Duplicate and skipped rows are identified before paid verification and do not consume verification credits. Completed unique checks, including unknown outcomes, use credits.