Mailto

MAILTO is a Uniform Resource Identifier (URI) scheme used to create hyperlinks that prompt the user's mail client to compose a new message. It is defined in RFC 6068, with earlier specifications in RFC 2368, and allows pre-populating recipient fields and headers such as subject and body.

Syntax: mailto:to-addr?[query]. The to portion can include one or more addresses, separated by commas. The query string encodes message headers using URL encoding, including subject, body, cc, and bcc. Example: mailto:[email protected]?subject=Hello&body=How%20are%20you%3F. Multiple recipients may be specified in the to field or via the cc/bcc parameters. Attachments are not carried by the mailto scheme; support for attachments depends on the mail client and is generally not reliable.

Behavior: Activating a mailto link launches the system's default email client or a webmail compose window, depending on user configuration and software. Some environments may not have a mail client installed, in which case the link may do nothing or open a webmail gateway. Because content is exposed in the link, large headers or sensitive data should be avoided.

Security and privacy: Mailto links can be harvested for spam if they appear on web pages, and pre-filled content can be manipulated for phishing or abuse. Users should be aware that content in the link may be visible in browser history and page source.

See also: email, URI schemes, RFC 6068. Notes: For detailed syntax and edge cases, refer to RFC 6068.