Import your contacts from a CSV

The fastest way to build your audience is to import a CSV, which is a spreadsheet saved as .csv.

Prepare your file

• Save your spreadsheet as CSV. Excel and Google Sheets both offer it under Export or Download.
• Include a header row with at least an email column. Common extras are first name, last name, and any custom fields you use.
• One contact per row.

Import it

1. Go to Audience and click Import.
2. Choose your CSV file.
3. Thunk Mail detects your columns and maps them to fields like email and name. Adjust any mapping that looks wrong.
4. Confirm to start the import.

Large files run in the background. Carry on working and check the import history when it finishes.

What Thunk Mail does on its own

• Detects duplicates, so the same person isn't added twice.
• Flags invalid or undeliverable addresses and skips them.
• Blocks disposable and throwaway domains that damage deliverability.
• Counts only valid, reachable contacts toward your plan's contact limit.

Fewer contacts imported than rows in your file?

That's normal, and the report tells you why. Open your Audience page, use the dropdown menu, and click Import History, then download the report for that import. It lists every skipped address and the reason.

Best practices

• Only import people who expect to hear from you: customers, signups, opt-ins. Purchased and scraped lists produce spam complaints, and those damage deliverability for everyone.
• Clean the file first. Obvious typos and addresses you already know are dead cost you nothing to remove now.

Next: Why was my contact blocked? explains each reason an address gets refused.