How to use mail merge

September 18, 2023
7 minutes

In this article we’re going to review what mail merge is and how to use custom variables to personalize your direct mail with LettrLabs.

What is Mail Merge

Mail merge is a feature that allows you to create personalized letters for multiple recipients using a template and a data source.

The design part of our letter creation page will be your template.

Your data source is a file that contains the information you want to insert in your letter, such as names, addresses, or a custom message.

How to Use Mail Merge and Custom Fields

To utilize this feature, we will be going over 3 topics.


  • You are able to add variables to your letter during the design phase of the letter creation. These variables will be replaced by the information you will provide in your data source.
  • To add a variable in your message, simply click inside of the message field for the variables to appear, then click on the variable you will be using.

Data File (files can be in CSV, XLSX, or XLS format)

  • Here is a sample template you can use when creating your dataLettrLabsUploadTemplate.csv
  • Necessary information that should be included in your data would be: First Name, Last Name, Address 1(for street addresses), Address 2(only necessary if address has an Apartment number, suite number, building name, floor number etc.), City, State, and Zip Code. These information should be separated into individual columns.
  • If you have inserted other variables to your letter like To Organization, Salutation, or Custom, remember to add them into your data as well in its each individual columns.
  • All the information provided in your data will be used as our mailing list. It will also be used to fill up the variable you have inserted into your letter.

Take note of this image. We have {First Name}, {Address 1}, and {Custom 1} variables inserted.

These variables will be replaced by the information you will be providing in your data.

Finished product would look like this.

Here is a sample video in action to show you the steps above


  • On the “Recipients” part of the letter creation, where you will upload your Data File, there will be a step where you would need to map your data.
  • This step is important to make sure  your information corresponds to a specific variable. Basically, all you need to do is match the Template Field with the Columns in your File.
  • We understand that you might already have existing files with information of your recipients. The Mapping feature would be very helpful in this situation especially if you have your columns named differently. Yes! It is not necessary that you have each column named like First Name, Last Name, or Custom 1-3. Check Images below for example.

Instead of this:

You might have it named like this in your existing data that don't match our data structure, and thats okay!

All you would need to do is to map it correctly. It will look like this:

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