Make a correctly encoded mailto: link with recipients, cc, bcc, subject and a multi-line body — as a URL, HTML or Markdown — or decode one you found. Runs in your browser.
Fill in at least one field, then build.
Mail apps differ. A mailto: link only pre-fills a draft in whatever mail app the visitor has set up; nothing is sent until they press send. Some apps ignore cc, bcc or body, and very long links can be cut off. Addresses in a public page's mailto: links can be collected by spam bots.