What is Mail Merge?

Mail merge is the process that streamlines the creation of multiple personalized emails, labels, or other documents from an already-existing template.

With mail merge, you can target specific customers to send out relevant information tailored to your audience’s needs —  without creating new content each time. 

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What can you use mail merge for?

Users use mail merge to automate the process of sending personalized bulk mail. It allows users to create multiple documents at once by connecting a pre-built template with a database of names and contact information. It’s often used along with other software and databases such as Microsoft Word, Microsoft Excel, Outlook, Gmail, and Google. 

The automatic process generates large batches of personalized emails or physical correspondence (letters, labels, and envelopes) by pulling data from a spreadsheet and inserting it into the corresponding section of a document. 

Mail merge can be used for both personal and business purposes, such as sending out wedding invitations, creating mailing lists for marketing, or designing personalized messages for customer loyalty campaigns.

We have millions of emails sent each week. Nylas frees us up to focus on other roadmap priorities, such as delivering new features to our customers and working with our data science team on exciting new projects.

Nora Ignatius

Product Manager, Salesloft

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Mail merge features and capabilities

Conditional options

Conditional options allow recipients to receive their emails based on conditions set by the user. 

For example, if you send out an email to customers who have bought a certain product, you can use conditions to ensure that only customers who’ve completed the purchase will receive the message. This feature makes it easier to segment your recipients and ensure they get relevant content.

Attachment options

Mail merge allows users to add customized attachments for each recipient in addition to the main message body text. 

This makes it easier for them to share personalized product catalogs or other detailed information without having to manually include those items in each individual message.

Users can also upload files directly from their computer or cloud storage services such as Dropbox and Google Drive.

Template customizations 

Mail merge offers several template customizations so users can further personalize their messages and documents as needed.  These templates can be used repeatedly without having to recreate them all the time. 

Users can add images and logos that match the content in their document, adjust font sizes and colors, insert hyperlinks into text blocks, and more. 

Mail merge templates and functionality help reduce manual, repetitive work for the end user. But, building email functionality can be time-consuming for development teams to create. 

How do you get mail merge functionality without spending thousands of hours to build the functionality? By using an email API. 

Email APIs are a set of protocols and tools that allow developers to quickly and easily integrate email functionality into their applications. With an email API, developers can stand up features that let users send and receive emails, retrieve email messages, manage email addresses, and perform other email-related tasks (like mail merge) all within an organization’s platform. 
For example, users with experience in development can take advantage of the Nylas APIs in order to create a mail merge template application using Ruby and the web framework Sinatra.  Our developer advocates share their insights into this process in an upcoming series of blog posts.

Start here: How to Create a Mail Merge Template with Ruby.

Importance of mail merge

The importance of mail merge is undeniable in today’s ever-evolving digital environment. Not only does it save time and money, but it also enables personalization opportunities that result in an improved customer experience. 

For high-volume sends, using a mail merge template is the right choice. 

Time & cost optimization 

Mail merge shortens the time spent customizing mass emails, eliminates manual data entry, and creates a unified customer-accessible database. Businesses can effectively manage email campaigns, track customer preferences and activity, and measure response rates quickly. 

Personalization opportunities 

Mail merge enables businesses to personalize content for each recipient. This might mean including the recipient’s first name in the body of the email or letter or sharing personal details with them (such as their recent purchases). This helps increase customer satisfaction and loyalty while also helping you improve your conversion rate.

How to mail merge

While mail merge varies based on the tool you’re using, the process follows these three primary steps:

Step 1: Prepare your data source

  • Gather the data that you want to use in the mail merge. Typically, the data is stored in a spreadsheet and exported to a CSV.
  • Format the data in the spreadsheet to organize it easily for the mail merge. That means including all the fields you use in your template and splitting each field into a new column. This means creating the template and the data source can be interchangeable steps.

Step 2: Create your template

  • Create the document you want to use as the template for the mail merge, such as a letter or email. It should include placeholders (fields) for the information you want to merge.
  • Insert placeholders where you want the data from the spreadsheet to be inserted.

Step 3: Connect your template to your data source and merge

  • In the mail merge software, link the template document to the data source.
  • Use the preview function to check that the merge works as expected and make any necessary adjustments.
  • Once you’re satisfied with the preview, you can complete the merge and output the results to a new document; which can be an email, or a mailing label.

Experience Nylas’ powerful API for your mail merge.

Sign up for a Nylas developer account and automate mail sorting, data entry, and data syncing from your users’ inboxes, calendars, and address books.

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How Nylas can help with mail merge

If you’re looking to make the mail merge process simple and painless for your users, use the Nylas Email API. Nylas can help you save time and quickly implement mail merge into your CRM or any other platform that sends out personalized communications. 

Additionally, Nylas offers APIs for calendar and contacts data. Our platform accelerates product velocity, allowing you to launch customizable communications workflows in a fraction of the time.

Let us handle mail merge, so your technical team can get back to building a world-class application. 

Talk to an expert and get a quote now

Frequently Asked Questions

What is mail merge?

Mail merge allows you to send personalized messages and communications to multiple recipients. Mail merge combines a main document, typically a form letter, with data from a database or spreadsheet, and each letter is individually tailored to the recipient’s details.

What documents can you make with mail merge?

Mail merge is a great way to create personalized, automated documents such as:

  • Letters
  • Envelopes
  • Labels
  • Emails
  • Postcards 
  • Mass-marketing materials

What is the mail merge formula?

The basic formula for mail merge is:

[Data Source] + [Standard Document] = [Personalized Documents]

  • Create or import your data source, which contains the information you want to use in your mass communications.
  • Create a template (such as a letter or email) using Microsoft Word/Excel/Outlook or Google Sheets/Gmail merge tools. 
  • Use the merge tools to combine the data from your data source with the template, creating personalized docs for each recipient.
  • Review and edit the merged documents as needed, and then send or print the communications.

What are mail merge conditions?

Mail merge conditions are rules used to filter and organize data when generating documents using mail merge. These conditions can be based on specific field criteria, such as name or address, the document language, or the current date and time. 

How to do an Outlook mail merge?

When using mail merge in Microsoft Outlook, you can use data sources that you’ve created in Word/Excel. You can also use other sources like Access or Outlook contact lists. After choosing what data source to use, then: 


  1.  Open Microsoft Outlook and select “new email” in the home tab. In the window that appears under mailings, select “start mail merge” and choose “email messages” from the dropdown menu. 
  2.  On this new window, click “select recipients” and choose either “use existing list” if you already have your contacts saved or “type new list” if you need to input them into this window manually. Click “ok” when finished. 
  3.  Now that your contact list has been selected, it’s time to write your message content. Select “insert merge fields” to add personalized information for each recipient into your email template. If desired, you can insert images or other media into your emails by clicking on Insert > Picture from the ribbon at the top of the window. 
  4. When ready, select “preview results” to ensure that everything looks good before sending out the mass emails! If any changes need to be made, simply make them here.
  5.  Finally, once everything looks good, it’s time to send out those emails! To do so, click on Finish & Merge > Send Email Messages from within Microsoft Outlook which will prompt another window asking how many recipients should receive each individualized message — select everyone and then hit send when ready!

Read the step-by-step instructions for How to Mail Merge in Outlook 

How to mail merge in Gmail/Google?

  1. Create (using Google Sheets), or import a list of contacts to send the email to. Once the contact list is established, it needs to be formatted into an appropriate form for use in Gmail. The easiest way to do this is using comma-separated values format (CSV). 
  2. Open up your Gmail account and navigate to Contacts in the main menu. Click on “more” and select “import” from the dropdown menu. From there, you can upload your contact list and save it as a group (this will make sending out emails easier later). 
  3. To create your mail merge message, you’ll need two documents: one containing all of the content for your message, including any placeholders you want to be included — and one containing all of your recipient information, such as names, email addresses, etc. Create these two documents and save them together as a single file that you can pull up on Google Docs or Microsoft Word.
  4. Open up Google Drive (or whichever platform you saved your files on) and access both documents side-by-side within the same window. On Google Drive specifically, you should select “open with > Google Docs” for each document so they can appear in the same window. Here you should copy over any placeholders from your main message document into the recipient document so that they have their own corresponding fields when merged together.  
  5. Once everything looks good, go back to your Gmail account and select “compose” from the main menu at the top of the page. Select “insert merge field” at the bottom left corner of the text box, which will bring up a pop-up window allowing you drag-and-drop any elements from either file into your email composition area; this way, all elements appear exactly how they were created within those original two files. 

After merging everything, hit send. Your email has now been sent out to everyone on that contact list with personalized content specific to each recipient. 

The Nylas Email API also supports mail merge with Gmail. With customizable templates and personalized attachments, mail merge has never been easier.

How to mail merge in Microsoft Word & Excel?

While this process isn’t supported by Nylas, it’s a popular way to create physical letters and envelopes that you’d send out manually. Here’s how to mail merge with Microsoft:  

  • Prepare your data source:
  • Open your Excel spreadsheet and make sure that your data is organized.
  • You want to ensure that the data is organized in columns and that the column headers clearly describe the information in that column.
  • Also, if you want to merge the name and address, ensure that the name and address fields are in separate columns.
  • You can then save your excel file in a format like .csv for easier and seamless use in the mail merge process.
  • Create your template document:
  • Open a new Word document and create the layout and design of your template document, including the text and images that will be the same for each merged document.
  • Insert merge fields into your document where you want the unique data from your data source to be inserted.
  • In Word, you can do this by clicking on the “mailings” tab, then clicking on “insert merge field,” and selecting the field you want to merge.
  • You can also use field codes, like this {MERGE FIELD FieldName } to insert the fields.
  • Link your template document to your data source:
  • With your template document open in Word, click on the “mailings” tab and then click on “select recipients.”
  • Select “Use an existing list” and then browse and select your data source file.
  • Preview the merged documents and make any necessary adjustments to your template document or data source.
  • Once everything looks good, click on the “finish & merge” button and choose to either “print” the merged documents, “edit individual documents,” or “send an email.”

And that’s it! You have just mail-merged your document. You can then print or send it to your desired recipients. 

Note: The process can differ depending on the version of MS Word and Excel you’re using, so the layout and tools of the menu might be different. But the concept and overall process are the same.

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Additional Resources

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10+ best email APIs in 2023 for developers [free & paid]
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