What Is Mail Merge? How It Works and Where It Stops Working

Mail merge is a way to send one message to many people, with each copy carrying that person's own details. You write the template once, connect it to a spreadsheet, and the software makes one email or letter for every row.

In Harrogate, Sophie Turner teaches piano to 180 families. Her term-start email reads "Hi «First name», «Pupil»'s lessons this term are on «Day» at «Time»." The merge turns that one template into 180 separate emails, one for each family.

What is mail merge?

Every mail merge has four parts: a template, a data source, merge fields and the output.

Part	What it is	In Sophie's term email
Template	The text that stays the same for everyone	The term dates and the school's address
Data source	A spreadsheet or contact list, one row per person	Her booking export: 180 families
Merge fields	Placeholders linked to columns in the data source	«First name», «Pupil», «Day», «Time»
Output	One finished copy per row	180 emails, each to one family

Merge fields go by other names. Gmail calls them merge tags, and email platforms usually say personalisation tags. Each one swaps a placeholder for the value in that person's row.

A merge field changes a word or a line. Dynamic email content goes a step further and changes whole sections of an email for different readers.

How does mail merge work?

The steps are the same in Word, Gmail and other tools:

1. Prepare the list with a header row: one column per detail, including one for email addresses.
2. Write the template and insert a merge field wherever a personal detail belongs.
3. Preview several rows to catch blank cells and odd values.
4. Run the merge, which sends or prints one copy per row.

Where you start depends on the software. In Word, the command sits on the Mailings tab under Start Mail Merge. In Gmail, it is the Use mail merge button beside the To line.

Excel sends nothing on its own. It holds the list for a Word merge, while Gmail reads its list from a Google Sheet. So a mail merge in Excel usually means a Word merge with an Excel spreadsheet as the data source.

Blank cells cause the most visible mistakes. A family with no first name on record gets "Hi ," unless the tool lets you set a fallback word such as "there". Gmail asks for one when a merge tag has no value.

Is mail merge still used?

Yes. Microsoft still builds mail merge into Word, and Google added it to Gmail, where it replaced the older multi-send mode.

It remains the quickest way to print addressed letters, labels and envelopes, or to email a few hundred people you already deal with. Sophie's term email, sent once a term to current families, is that kind of job.

It also keeps a list private. Each person gets their own copy, so nobody sees the other addresses.

That makes it safer than BCC (blind carbon copy), where one slip into the CC field exposes the whole list. In its guidance on email and security, the Information Commission's Office (ICO) asks organisations to consider mail merge or bulk email services rather than BCC.

Mail merge in Word, Outlook and Gmail

The three common routes share a name but behave differently. Only Word and Gmail fill in personal fields, and their limits, as Microsoft and Google documented them in October 2026, compare like this.

Word with classic Outlook

Word hands each merged email to a desktop email program, usually classic Outlook for Windows. Every address gets its own message, and Microsoft notes that nobody else can be copied in with CC or BCC (Microsoft Support).

Mail merge in new Outlook

New Outlook cannot send Word's merge, and its own Start mail merge sends identical copies with no personal fields (Microsoft Support). The fix, the steps and Microsoft's sending limits are set out in how to do a mail merge in Outlook.

Gmail mail merge

Gmail's mail merge is built in, but only on eligible paid Google Workspace plans such as Business Standard and Business Plus. A free personal Gmail account does not have it.

You type @ to add merge tags such as @firstname, or link a Google Sheet and use any of its columns (Gmail Help).

Two limits catch people out. Merge tags do not work in the subject line, and you cannot schedule a merged message.

Where mail merge stops working

Mail merge stops working when a one-off note turns into regular marketing to a growing list. Sophie reaches that point with her summer concert. She wants to sell tickets and promote a holiday workshop to 1,900 current and former families.

Daily sending limits

A merge sends from your own mailbox, so your mailbox's limits apply. At 1,500 merge recipients a day, Gmail would need two days for Sophie's list.

Microsoft 365 allows a mailbox 10,000 recipients a day but only 30 messages a minute (Exchange Online limits, updated 19 October 2026). At that pace, 1,900 merged emails need more than an hour to leave the outbox.

No record of who unsubscribed

UK marketing emails must give people a working way to opt out, in every message. Under the Privacy and Electronic Communications Regulations (PECR), you also need consent or the soft opt-in before you send marketing to individuals (ICO).

A Word merge has no unsubscribe link. Every "please take me off your list" reply has to be spotted and marked in the spreadsheet by hand before the next merge.

Gmail emails you each time someone uses its unsubscribe link. It cannot give you a list of everyone who left, though, and the opt-out does not cover emails you later send without mail merge.

Sophie's term-time email sits outside these rules. The ICO says routine customer service messages, such as information about a current contract, do not count as direct marketing. The concert email sells tickets, so it is marketing.

None of this is legal advice; the UK GDPR and PECR rules for email marketing are set out in more detail.

No results to learn from

A merge records what was sent, not what happened next. Sophie cannot see which families clicked the ticket link, and bounce notices land in her inbox one at a time.

Your everyday address takes the risk

A merge goes out from the address and domain you use for invoices and replies. If enough families mark the concert email as spam, mailbox providers can start filtering that domain's everyday email too.

Gmail, Yahoo and Microsoft publish requirements for email senders on authentication and spam complaints.

Microsoft's limits page points this kind of sending elsewhere. It tells customers who send legitimate bulk commercial email, such as newsletters, to use third-party providers that specialise in it.

What has replaced mail merge?

For marketing email, email marketing platforms have replaced mail merge. They keep the merge idea of a template filled from a list. They add what a merge lacks: unsubscribe handling, reports and sending infrastructure built for volume.

Outside marketing, the answer differs. Sales teams who write one-to-one emails tend to use the sequences in their CRM (customer relationship management system) instead.

Sophie's concert email is a classic eshot: one marketing email to a whole list, the job an email platform is built for.

Moving a mail merge list into MailGraf

Sophie's spreadsheet moves into MailGraf without retyping, and her merge fields become personalisation tags.

1. Open Imports, click New import and choose a target list. Upload the spreadsheet as a CSV, Excel (.xlsx) or text file.
2. On the Mapping step, match each column to a field: Email, First name or a custom field such as Lesson day. Create custom fields first under Fields.
3. On the Permission step, tick I confirm these contacts gave me permission to email them. Contacts from a file are recorded as single opt-in.
4. Run a second import with Upload unsubscribed contacts as the import type for anyone who left earlier merges.
5. Former families' addresses can be years old, so run the free bounce test under Reports > Email verification before the concert email.
6. In the email editor, click Insert tag to place a field, and type a default value such as "there" for contacts without a name.

The file import help article explains the result report, duplicates and skipped rows.

In MailGraf, the footer with the Unsubscribe link cannot be deleted from a design, and unsubscribed or blocked contacts are always left out of the audience.

After the send, View clickers on the ticket link, in the report's Click map, lists the families who used it (Read a campaign report).

For a domain you own, MailGraf recommends sending campaigns from a subdomain, such as news.yourschool.co.uk, which keeps campaign sending apart from everyday email.

With no daily sending cap on the monthly plan, the concert email reaches all 1,900 families in one send, not across the two days Gmail's merge would need. Sophie can then create her MailGraf account and follow the import steps above.