Google has created this webpage below to guide how to implement Mail Merge using its built-in Google Docs scripting tools.
You may find it difficult to use at first if you do not have background to programming, but trust that once you created the first one, it will be quite easy to use for the second and the rest.
Please test with a few internal contacts first to ensure correct of codes and contents. Once you are confident, you may use it to send out to real recipients.
Note: If you expects to send a large number of mail merge recipients, please kindly review Google's policy on their sending limits
Please do not hesitate to contact IT Team for help if needed.