Use a clear header row, one contact per row, and separate columns for email, person, company, and domain context.
Recommended spreadsheet columns
Include an email column and, where available, first name, last name, title, company, company website or domain, source, and last-reviewed date. Keep one value per field so the file can be mapped consistently.
Save the file as CSV using UTF-8 encoding.
Keep one contact per row and a single header row.
Remove blank rows and obvious duplicate records.
Do not place several email addresses in one cell.
Keep source and company context instead of uploading a bare address list.
What should I do before upload?
Confirm that the file is authorized for your business use, remove columns you do not need, and back up the original. Normalize obvious whitespace and domain formatting without inventing missing emails. Apply existing opt-out and suppression data before preparing a campaign.
How should I use the result?
Keep likely-existing, catch-all unresolved, inconclusive, and likely-invalid rows separate. Preserve the original row and append status, reason, and checked date rather than overwriting your source data. Send unresolved contacts to enrichment and suppress unsupported addresses from normal outreach.