You can use Google calendar to send recurring emails. G-Suite Calendar is of course available no cost.  No HTML--so users will need to "copy and paste url into browser window". I use google url shortener and create a short cut phrase ""  then paste in the unique alphanumeric string to follow the final forward slash, e.g., takes you to Silviesrcs support solutions page.

Here's a five minute How to video to use Google Calendar to send recurring messages:

Thanks for sure,

Silvies IT