How to Send Personalized Attachments in Bulk Emails with Gmass

If you’re sending the same email to a big list but each person needs their own attachment—like a different invoice, report, or certificate—it can get messy fast. Doing it by hand? Forget it. Most email tools can’t handle personalized attachments, or hide the feature behind a paywall, or make you jump through way too many hoops.

This guide is for anyone who actually needs to send unique files to lots of people at once—without breaking the bank or wasting a weekend. We’ll walk through how to do it with Gmass, a Gmail mail merge tool that’s surprisingly good at this (with a few quirks you should know about).

Let’s get your bulk emails out—attachments and all—without losing your mind.

Why Personalized Attachments Are a Pain

Before jumping in, let's be clear: adding attachments to mass emails isn’t hard. Adding different attachments for every person? That’s the tricky part. Most bulk email tools only let you send the same file to everyone, or they make you write scripts, use APIs, or pay extra for “advanced” features.

Why bother? - You need to send invoices, contracts, or certificates tailored to each contact - You want to avoid sharing everyone’s private info in a big group email - You want it done in Gmail, not a fancy CRM

Gmass isn’t the only tool out there, but it’s one of the few that makes personalized attachments doable for non-coders. There are some trade-offs, but if you stick to the steps below, you’ll save yourself hours.

What You’ll Need

Before you start, make sure you have: - A Gmail or Google Workspace (G Suite) account. Gmass works as a Gmail add-on. - A Gmass account. The free tier is limited; you’ll need a paid plan for attachments. (Check their pricing—don’t get surprised.) - A Google Sheet with your email list. This is where you’ll keep contact details and attachment info. - Your files to attach—already named and uploaded to Google Drive. You can use files stored elsewhere, but Drive is easiest. - Patience for a few quirks. No magic here—just a little setup.

Step 1: Prep Your Google Sheet

This is where most mistakes happen, so take your time here.

  1. Set up columns for each mail merge field.
    • At minimum: Email (recipient), FirstName (optional), and Attachment (see below).
  2. In the Attachment column, put the full Google Drive link to each recipient’s unique file.
    • It has to be a direct link to the file, not just the folder.
    • Double check the links—typos here mean missing files later.
  3. Make sure each Drive file is shared so Gmass can access it.
    • Either “Anyone with the link can view,” or at least, shared with your sending account.
    • If Gmass can’t access the file, the attachment won’t send (and the recipient gets nothing).

Pro Tip:
If you have a ton of files, use a formula to build links. For example, if files follow a pattern like Invoice_JohnDoe.pdf, you can build the link based on the name column.

Step 2: Connect Gmass to Your Sheet

  1. Open Gmail in Chrome. (Gmass works best in Chrome.)
  2. Click the Gmass button (the red spreadsheet icon) next to the search bar.
  3. Pick your Google Sheet.
    • Gmass will show a list of your Sheets. Select the one you just prepped.
  4. Gmass will pull in your recipients. If you see errors, fix your Sheet.

Honest Take:
Gmass can be fussy about Sheets—column headers have to be perfect, and weird formatting can break things. If the import fails, check for merged cells, blank rows, or extra spaces in headers.

Step 3: Compose Your Email with Merge Tags

  1. Click “Compose” in Gmail.
  2. Write your message as usual. Use curly brackets for merge fields, like {{FirstName}}.
  3. Don’t attach any files manually. Gmass handles this from the Sheet.

Example:

Hi {{FirstName}},

Attached is your invoice for this month. Let me know if you have any questions.

Thanks, Your Name

Pro Tip:
Test with just a few rows first so you don’t spam your whole list if something’s off.

Step 4: Tell Gmass to Use Personalized Attachments

Here’s where the magic happens.

  1. In your Sheet, make sure the column with links is called “Attachment” or “Attachments.”
    • Gmass looks for this exact header.
  2. If you want to send multiple files to each person, separate links in the cell with a comma.
    • Example: https://drive.google.com/file/d/12345, https://drive.google.com/file/d/67890
  3. Back in Gmail, click the little arrow on the Gmass “Send” button.
    • Choose “Send Test Email.” Verify the right attachments are there.
  4. If all looks good, hit “Gmass” to send to your list.

Heads-Up:
Gmass sends one email per recipient, each with their own attachment(s). There’s no way to show a “preview” of every message, so always test first.

Step 5: Check Results and Troubleshoot

Don’t assume it worked—check your “Sent” folder and ask a friend (or your own alternate email) to confirm attachments came through.

Common Gotchas

  • Attachment missing?
  • The file link is wrong, or sharing settings are too restrictive.
  • Wrong file sent?
  • Double-check the Sheet—maybe you pasted the wrong link.
  • Gmass errors out or skips rows?
  • Usually a Sheet formatting issue. Clean up blank rows, merged cells, or weird characters.
  • Hitting Gmail send limits?
  • Gmass can’t break Gmail’s daily limits (usually 500/day for regular accounts, ~2,000 for Workspace).
  • Files too big?
  • Gmail attachments have a 25MB total limit per email (including body). If you go over, the email won’t send.

Pro Tip:
If you need to send a ton of big files, consider sending links instead of attachments.

What Works, What Doesn’t, and What to Ignore

What works: - Sending unique files from Google Drive to each recipient, no coding required. - Works for PDFs, Word docs, images—anything Google Drive can store. - Merge fields in the email body (names, custom info) work as usual.

What doesn’t: - Files stored only on your hard drive; you must upload to Drive or use direct URLs. - Sending huge files or batches (over Gmail limits)—Gmass can’t work miracles. - Showing a fancy preview of every email before it sends. (You get one test at a time.)

What to ignore: - Any advice about “attaching files manually” for each recipient. That’s not scalable. - Workarounds using Google Apps Script unless you like debugging code for fun.

Quick FAQ

Can I send attachments from Dropbox or OneDrive?
Sort of. You can paste direct download links in the Sheet, but Google Drive is much smoother.

Can I send multiple attachments per person?
Yes. Separate the links with commas in the Sheet.

Does Gmass cost money?
Personalized attachments require a paid plan—not available on the free tier.

Are attachments secure?
As secure as your Google Drive sharing settings. Set files to “Anyone with the link can view” only if privacy isn’t a concern.

Keep It Simple—Iterate as You Go

Mail merges with attachments aren’t rocket science, but they’re easy to mess up if you rush. Start with a tiny test list, triple-check your Sheet, and don’t overcomplicate things. Gmass isn’t perfect, but for this use case, it beats the alternatives (or worse, doing it by hand).

Refine your process as you go—and remember: most people just want the file. Don’t stress about making it fancy.

Happy sending!