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Mail Merge

Emails and letters from one sheet

A Google Sheets add-on that sends personalised emails and creates letters from one spreadsheet, without data leaving the company's Google account.

FinanceGoogle Sheets add-onBuilt with Claude Code

The problem

The finance team needed to send personalised payment updates and formal letters from spreadsheet data. Paid mail-merge tools meant another subscription and wide permissions over company data.

What it does

  • Sends personalised emails through Gmail, using a Gmail draft as the template.
  • Creates personalised letters as PDF or Word files, saved to a Drive folder.
  • Checks the data first and highlights problem rows in the sheet itself.
  • Logs every send in a new column, so there is a record of who got what.

Why I built it this way

  • Templates are Gmail drafts, so the team writes them in a tool they already know.
  • Placeholders such as {{first_name}} match the column headers automatically.
  • The send log never overwrites: each batch adds a new column.
  • No open or click tracking, and no data leaves Google Workspace.

Screens

Mock-ups with made-up sample data.

The email Priya receives.

Choosing a template. The template is a Gmail draft. Merge fields come from the column headers, and any row can be previewed before anything is sent.

The send log, written into the sheet.

Checking the data. Problem rows turn red in the sheet, the sidebar says what is wrong with each one, and the send log is written into a new column.