RFC 2368 (rfc2368) - Page 2 of 10
The mailto URL scheme
Alternative Format: Original Text Document
RFC 2368 The mailto URL scheme July 1998
mailtoURL = "mailto:" [ to ] [ headers ]
to = #mailbox
headers = "?" header *( "&" header )
header = hname "=" hvalue
hname = *urlc
hvalue = *urlc
"#mailbox" is as specified in RFC 822 [RFC 822]. This means that it
consists of zero or more comma-separated mail addresses, possibly
including "phrase" and "comment" components. Note that all URL
reserved characters in "to" must be encoded: in particular,
parentheses, commas, and the percent sign ("%"), which commonly occur
in the "mailbox" syntax.
"hname" and "hvalue" are encodings of an RFC 822 header name and
value, respectively. As with "to", all URL reserved characters must
be encoded.
The special hname "body" indicates that the associated hvalue is the
body of the message. The "body" hname should contain the content for
the first text/plain body part of the message. The mailto URL is
primarily intended for generation of short text messages that are
actually the content of automatic processing (such as "subscribe"
messages for mailing lists), not general MIME bodies.
Within mailto URLs, the characters "?", "=", "&" are reserved.
Because the "&" (ampersand) character is reserved in HTML, any mailto
URL which contains an ampersand must be spelled differently in HTML
than in other contexts. A mailto URL which appears in an HTML
document must use "&" instead of "&".
Also note that it is legal to specify both "to" and an "hname" whose
value is "to". That is,
mailto:addr1%2C%20addr2
is equivalent to
mailto:?to=addr1%2C%20addr2
is equivalent to
mailto:addr1?to=addr2
8-bit characters in mailto URLs are forbidden. MIME encoded words (as
defined in [RFC 2047]) are permitted in header values, but not for any
part of a "body" hname.
Hoffman, et. al. Standards Track