If you are using Mozilla Thunder bird as a mail client, you can use it for Mail merge too. Fot this you can install an add-on named “Mail Merge”.
Thos will you give you 2 options
1. To Mass mail : This will help you to send one mail to More than 100 contacts. You can add all your contacts to TO,CC or BCC fields and send.
2. Personal Mail: This is exactly like Mail Merge. It will read a csv file and will replace the corresponding fields in the email with values and will send individual emails to each contacts.
Example (CSV):
ID,Name,Mail
1,"John Doe",john.doe@example.com
Example (Draft):
To: {{Mail}}
Subject: Your Membership (ID: {{ID}})
Body: Hallo {{Name}}, your membership is confirmed!
Example (Mail):
To: john.doe@example.com
Subject: Your Membership (ID: 1)
Body: Hallo John Doe, your membership is confirmed!
Read more and get the extension here