Yet Another Mail Merge (YAMM) is an add-on to Google Sheets available to @umd GSuite users. It provides an easy way to send out up to 1,500 emails per day. It has useful additional features, such as tailoring certain details of the mass emails to users, including a clickable button to a link (such as making a simple Yes/No response), and tracking the progress of the email (how much it is read).

You can watch a quick overview here, to learn more.

YAMM functions by having you make your draft email, then putting the contacts into a Google Sheet. If your email includes customized data, can then customize certain details of the email in the google sheet to each contact, if you choose to.

Steps to installing YAMM can be found here.

Below is the link to the getting started documentation.
https://support.yet-another-mail-merge.com/hc/en-us/categories/201313669-Getting-Started