How to send a mail merge with attachments from Gmail

First: the same file, or a different one for each person?

These are two different jobs, and most tools do only one of them well.

• The same file for everyone: a brochure, a price list, an invitation, an agenda. Almost every mail merge tool can do this, and you attach the file once.
• A different file for each person: an invoice, a certificate, an offer letter. Now the tool has to match each file to a row in your list, so you need one that does this on purpose, or a link in place of the file.

Decide which you have before you choose a tool.

Attach it, or send a link?

A link is often the better choice, and Google itself suggests a Drive link for mail merges. Here is how to decide:

If you do link, test the link in a private browser window. Many “you need access” replies come from a Drive file shared only with its owner.

How big can attachments be?

Google says the limit for personal Gmail accounts is 25 MB, and that for work and school accounts it is whatever their administrator sets. In Gmail itself, a bigger file is turned into a Google Drive link for you. A tool sending through your account can’t count on that, so a mail merge has to fit.

The catch is encoding. Email can carry only text, so files are converted to a text form called base64 on their way out, and every 3 bytes become 4. Your files grow by about a third:

So to stay under 25 MB once encoded, keep your files to about 18 MB. That matters most at the other end, because each receiving mail server has a limit of its own, and some refuse messages over 25 MB.

Fusomail takes up to 10 files and 20 MB an email. At the top of that range the encoded email is about 27 MB, which some receiving servers may refuse, so for the safest delivery stay at 18 MB or below. Smaller is better anyway: a campaign with a 15 MB file is slow to open on a phone. A PDF of a few MB is usually plenty.

File types Gmail refuses

Gmail blocks 54 file types outright, mostly programs and scripts, because they are how viruses travel. They include .exe, .bat, .cmd, .js, .jar, .msi, .vbs, .apk, .dmg and .iso.

Two rules catch people out:

• Hiding them doesn’t work. A blocked type is refused in compressed form (.gz, .bz2) and inside an archive (.zip, .tgz).
• Neither do passwords. Gmail also refuses password-protected archives that hold other files.

Fusomail refuses these when you add them, with the reason, and looks inside a .zip, so you find out now and not halfway through a campaign. To share something Gmail blocks, upload it to a cloud drive and send the link.

Allowed, but risky

Some types get through and still raise suspicion: archives, Office files with macros (.docm, .xlsm) and web pages (.html, .svg). The deliverability check lists 22 of them as worth a second thought. For a document, send a PDF.

Why attachments use more storage than you think

Each email in a mail merge is a separate email, so each one carries its own copy of the file. Google’s own example: a 10 MB file sent to 500 people uses about 5 GB of your storage.

That is true of any tool that sends through your Gmail, Fusomail included, because every sent email stays in your Sent mail. On a free Google account, with its shared storage, one big campaign can use up a lot of it. A small PDF, or a link, avoids the problem.

Fusomail keeps one copy of each file for the campaign itself, and that counts towards your plan’s storage (Free 25 MB, Starter 250 MB, Premium 1 GB, Pro 2 GB).

How to send the same file to everyone

In Gmail’s built-in mail merge

On an eligible Workspace plan, attach the file to your message as usual. It goes into each person’s copy. See the mail merge guide for the rest of the steps.

In Fusomail

1. Open a draft campaign or a template, and go to its content.
2. Drop your files on the attachments area, or choose them from your computer. A file Gmail would refuse is turned away here, with the reason.
3. Check the total against the 20 MB limit, and aim lower if you can.
4. Send yourself a test. The preview, the review step and the test email all carry the files.
5. Start the campaign. Files can’t be changed after that, so everyone gets the same ones.

Attachments are on every plan, free included, and files you use often can live on a template. See attachments in Fusomail.

How to send a different file to each person

Your choices, from simplest to most involved:

A link in a merge field

Upload each file somewhere it can be opened, put each link in a column of your list, and use the column as a merge field: {{invoice_link}}. This is how to do it in Fusomail today: it doesn’t attach a different file for each person, and a campaign’s files go to everyone in it.

Think about privacy here. A link that anyone can open is fine for a certificate, and not for a salary letter. Use a service that gives each person a private link.

An add-on built for it

Some tools match files to rows for you, which suits you if you really need a file in the email:

• YAMM attaches files from Google Drive, by a link in a column or by matching an ID in each file’s name, and turns Google Docs, Sheets and Slides into PDFs. Files must be in Drive and your list in a Google Sheet.
• Mail Merge for Gmail from Digital Inspiration says you can “send different attachments to different people”, also from Google Sheets.

Name your files with care. In YAMM’s matching, for example, an ID of “Chris” would match both Chris-Parker and Chris-Wilson; use something unique, such as an employee number.

Sending a link that actually opens

If you chose a link, the common failure is a reader who sees “You need access”. In Google Drive, a new file is private until you share it, so:

1. Upload the file, open its sharing settings and set general access to Anyone with the link, as a viewer.
2. Copy the link, and open it in a private browser window where you are signed out. If you can read it there, so can they.
3. Write a few words around it: “Here’s the price list (PDF, 2 MB)”. A bare address tells nobody what they are clicking.

Use the full address rather than a URL shortener: spammers hide behind shorteners, so filters look harder at them, and the spam word checker flags them for that reason.

Watch out for one thing in Gmail’s own merge: Google says merge tags can’t go in hyperlinked text, so a different link for each person has to be written out as an address. In Fusomail a field can hold the whole address, and works in a formatted link too.

Attachments and the spam folder

A file doesn’t send an email to spam by itself, but it does add risk. Spam and phishing mail often carries files, so filters and readers both look harder at them. Some rules of thumb:

• Don’t attach anything to a first email to someone who doesn’t know you. Offer it instead: “happy to send over the price list”.
• Say what the file is, in words, in the email.
• Give it a name a person would use: Pixelnest price list 2026.pdf, not doc_final_v3(1).pdf.
• Send PDFs, not archives or files with macros.
• Check your domain is set up: the SPF, DKIM and DMARC checker takes seconds.

A checklist for attachments

• Would a link do? If so, use one.
• Are the files under about 18 MB in total?
• Are they ordinary types, and if they’re archives, is everything inside allowed?
• Does the file name make sense to the person receiving it?
• Have you sent yourself a test and opened the file from the email, on your phone?
• If a link is used, does it open in a private window?