How to generate automatic mail !?

I need to generate an automatic mail to various recipients while clicking Tomy add-on .how to do this ?

What is this “Tomy add-on”? You want to do this in some webmail in Firefox?

sorry that is when i click to my addon

WebExtensions can’t send e-mails directly. SMTP is not supported and users usually don’t have their own mail server/domain/etc.

You can of cause use any number of HTTP APIs that in the end send mails. I know that MailGun supports browser-side usage of their APIs, which would work if you want the users to send mails from your domain, but I don’t know how it’s done (esp. how you keep your API keys secret). And spam could be a major problem.