Mail Merge with Individual Attachments (2025): YAMM vs GMass vs Mailmeteor vs Dropfill

So, you have a spreadsheet of 50 clients and a folder of 50 unique PDF invoices. You need to email each client their specific invoice.

It sounds like a simple task, but if you've ever tried to do this, you know it's a headache.

Gmail and Outlook don’t natively support mail merge with different attachments per recipient. They generally only let you send the same attachment to everyone. That’s useless for invoices, payslips, tickets, or personalized reports.

To solve this, you usually have to look for third-party tools. But which one should you choose?

In this post, we’ll compare the most common approaches—especially the tools people search for most: YAMM (Yet Another Mail Merge), GMass, Mailmeteor, and Dropfill—with a quick note on Outlook and automation workflows too. We’ll focus specifically on the individual attachment use case.

The Challenge: “Per‑Recipient Attachments Need a File Reference”

Most mail merge tools differ in one major way: cloud (browser) vs. desktop (local).

Tools like YAMM, GMass, and Mailmeteor live inside your browser (often as Chrome extensions and Google Workspace add-ons). They can’t automatically scan a local folder on your computer to find “Invoice_1001.pdf” and match it to row #1001.

So to send different attachments per recipient, you typically have to:

Upload the files to a cloud location (commonly Google Drive).
Put a Drive link or file ID (one per recipient) into your spreadsheet.
Configure the tool to attach the file referenced by that column.

It works—but it’s extra setup. And for sensitive documents, it also adds an extra “data handling” step (storage + permissions) you may not want. You often don’t need to make files public, but you do need to manage access correctly.

Let's look at the contenders.

1) YAMM, GMass, and Mailmeteor (Google Add‑Ons)

These are popular Gmail/Google Sheets mail merge tools. They’re excellent when your workflow already lives in Google Workspace—and when you care about “campaign-style” features.

How it works:

You upload files to Drive, put a Drive link/file ID in your sheet, and let the tool attach files based on that column. Some setups can be streamlined, but it’s still a spreadsheet-driven mapping step.

Pros:

Great for Google Workspace: Naturally fits Gmail + Google Sheets.
Campaign features: Many add-ons focus on tracking and follow-ups (varies by tool/plan).
Works anywhere: Once files live in Drive, you can run it from any computer.

Cons:

Attachment mapping overhead: You must maintain a per-recipient “file reference” column.
Cloud storage + permissions: Sensitive documents often end up in Drive (plus the add-on needs access).
Hard to use a local folder: No “select a folder and auto-match filenames” workflow.

2) Outlook Mail Merge & Automation Workflows (Common Alternatives)

People also try:

Outlook + Word mail merge (often with extra scripts/add-ins if attachments differ per recipient)
Automation builders like Zapier/Make + Gmail/SMTP (powerful, but you’re essentially building and maintaining a pipeline)

These can work, but they usually trade simplicity for setup complexity—especially once you add “unique attachments per recipient.”

3) Dropfill (Local‑First Desktop Automation)

Dropfill takes a different approach. It's a desktop app (for Mac and Windows).

Because it runs on your computer, it can see your files directly. This removes the whole “upload + file links” step for the common case where your PDFs already live in a folder.

How it works:

Import your Excel/CSV list.
Select the folder containing your files.
Choose a Match By column (Name, ID, Company, Invoice Number, etc.).

That’s it. Dropfill scans filenames in your folder and matches them to each row—then lets you preview each recipient before sending via Gmail, Outlook, or SMTP.

Pros:

Local-first privacy: No need to upload documents to Drive just to mail-merge attachments.
Fast setup: Point at a folder and match by a column—no link columns to maintain.
Operational-email focused: Built for invoices, payslips, reports, tickets—not newsletters.

Cons:

Desktop Only: You need to install an app (Mac/Win).
Not a marketing suite: If you need heavy campaign automation/tracking, a marketing tool may fit better.

Comparison Table

Feature	YAMM / GMass / Mailmeteor	Dropfill
Platform	Google add-on / extension	Desktop app
Per-recipient attachments	Usually via Drive link/file ID column	Match local files by filename
Where files live	Google Drive	Your local folder
Setup time	Medium–High (upload + mapping column)	Low (select folder + match by column)
Best for	Google-centric mail merges, campaigns	Invoices, payslips, reports, tickets

Summary

If you’re sending marketing-style campaigns (and attachments are the same for everyone), tools like YAMM, GMass, or Mailmeteor can be a great fit.

If you’re sending individual, private documents (payslips, invoices, tickets), Dropfill is built for that workflow: match local files to rows, preview, and send—without turning your folder into a Drive-link spreadsheet project.

Stop fighting with attachment mapping columns. Download Dropfill and finish your work in 5 minutes.