Check your mail merge before you hit send

Catch Hi ,, broken fields, duplicates and typo'd addresses, and see exactly what every recipient will get. Free, and nothing leaves Google.

Install from Google Workspace Marketplace

Or in Google Sheets™ choose Extensions › Add-ons › Get add-ons and search for “Mail Merge Pre-flight Check”. Questions: support@appgarden.co.uk.

The five emails you don't want to send

• Hi , — blank first names. How fallbacks fix it in every tool.
• Dear {{First Name}} — a tag with no column. Why fields don't populate.
• Someone else's invoice amount — a sorted column. How misalignment happens.
• The same email three times — duplicates. Duplicates, kept once.
• Half the list stuck at today's quota — the daily limit. Quotas, dated per tool.

Works with the tool you already use

Or any {{ }} / << >> merge. Not affiliated with Google or any merge tool.

Who it is for

What it checks

Every finding carries a rule code, so a result you read again in six months still says which check produced which line.

See the guide for what each check means and how to fix it by hand — free users can fix everything themselves.

Free vs Pro

Schools and charities: 50% off Pro.

Your data

Your list and template never leave Google. The checks run in the sidebar, in your browser. The only network traffic this add-on makes is to the licence server, and only a licence key and an anonymous install id ever cross it — plus domain names, only if you switch the mail-server check on. It asks for two scopes and nothing else: this spreadsheet only, plus the sidebar UI. It can't read or send your email. Privacy notice.

FAQ

Does it send email? No. It checks in front of your merge tool; your tool sends.

Does it change my sheet? Never. It only reads your list; every output goes to new tabs.

Which tools does it work with? Lists for YAMM, Mailmeteor, GMass and Gmail™ mail merge, or any {{ }} / << >> merge.

Is it an email verifier? No — and that is a feature. It never sends your addresses off-Google to be "verified". It checks what verifiers don't: the merge itself.

Does it work on desktop browsers? Yes — desktop browsers only. It does not run in the Google Sheets™ mobile apps.

Gmail™ and Workspace? Both.

Our admin blocks add-ons. Ask them to allowlist “Mail Merge Pre-flight Check” from the Google Workspace™ Marketplace; it requests this-spreadsheet-only access.

Is this a Google product? No. Mail Merge Pre-flight Check is published by AppGarden and is not affiliated with Google or any merge tool.

Articles

• Mail merge sent “Hi ,” — how to handle blank first names
• How many emails can I send with a mail merge from Gmail™ per day?
• Mail merge dates showing as numbers in Google Sheets™ (and £ going missing)
• Gmail™ mail merge fields not working? Check your column headers
• A pre-send checklist for school newsletters from Google Sheets™
• Check an email list for typos and duplicates in Google Sheets™
• The mail merge that sent the wrong details to the wrong person

Support

Email support@appgarden.co.uk. Include which finding looked wrong and, if you can share it, a copy of the list with the problem — read the privacy notice first.