A mail merge is the process of generating form letters and other Microsoft® Word documents that are personalized for the recipient, who is often a contact or lead. The content of each document is predefined in a mail merge template. Mail merge templates include variables called merge fields where data from your Salesforce records—for example a contact’s name and address—displays in the generated document.

1. Enable Extended Mail Merge in User interface.

2. Create Mail Merge Template document.

3. To get the template merge fields, use the below link

https://<yourdomain>.my.salesforce.com/servlet/servlet.SForceMailMerge?id=<SalesforceRecordId>

4. To enter the merge field use the below steps.

i. Go to Quick Parts –> Field.

ii. Select MergeField and enter the Field name.

Check the sample below.

5. Go to Communication Templates –> Mail Merge Templates.

6. Click New Template button.

7. Select the template created and Save it.

8. Go to Leads tab and select Mass Mail Merge under tools.

9. Select the lead records.

10. Select Documents or Envelope or Label. I have selected Documents since I created Documents template.

11. Click Finish.

12. Check your email for the document.