mailto URL specifies an email message to be sent to a given
email address. For example, ‘mailto:firstname.lastname@example.org’ specifies
sending a message to ‘email@example.com’. The “retrieval method”
for such URLs is to open a mail composition buffer in which the
appropriate content (e.g., the recipient address) has been filled in.
As defined in RFC 2368, a
mailto URL has the form
where an arbitrary number of headers can be added. If the
header is ‘body’, then contents is put in the message
body; otherwise, a header header field is created with
contents as its contents. Note that the
url library does
not perform any checking of header or contents, so you
should check them before sending the message.
The value of this variable is the function called whenever url needs to send mail. This should normally be left its default, which is the standard mail-composition command
compose-mail. See Sending Mail.
If the document containing the
mailto URL itself possessed a
known URL, Emacs automatically inserts an ‘X-Url-From’ header
field into the mail buffer, specifying that URL.