A header field in the mail buffer starts with a field name at the
beginning of a line, terminated by a colon. Upper and lower case are
equivalent in field names (and in mailing addresses also). After the
colon and optional whitespace comes the contents of the field.
You can use any name you like for a header field, but normally
people use only standard field names with accepted meanings. Here is
a table of commonly-used fields. Emacs pre-initializes some of these,
depending on various options you can set. You can delete or alter any
header field before you send the message, if you wish.
The address of the sender (you). This should be a valid mailing
address, as replies will normally go there. Emacs initializes this
field using the variables user-full-name and
user-mail-address; see below.
The mailing address(es) to which the message is addressed. To list
more than one address, use commas (not spaces) to separate them.
A piece of text saying what the message is about. Most mail-reading
programs can display a summary of messages, listing the subject of
each message but not its text.
Additional mailing address(es) to send the message to. This is like
‘To’, except that these readers should not regard the message as
directed at them.
Additional mailing address(es) to send the message to, which should
not appear in the header of the message actually sent. “BCC” stands
for blind carbon copies.
The name of one file, to which a copy of the sent message should be
appended. Emacs writes the message in mbox format, unless the file is
in Babyl format (used by Rmail before Emacs 23), in which case Emacs
writes Babyl. If an Rmail buffer is visiting the file, Emacs updates
it accordingly. To specify more than one file, use several ‘FCC’
fields, with one file name in each field.
An address to which replies should be sent, instead of ‘From’.
You can use this header if, for some reason, your ‘From’ address
is unable to receive replies.
This field takes precedence over ‘Reply-to’. It is used because
some mailing lists set the ‘Reply-to’ field for their own purposes
(a somewhat controversial practice).
This field contains one or more addresses. It is typically used when
you reply to a message from a mailing list that you are subscribed to.
It usually indicates that you want replies to go to the list, and that
you do not need an extra copy sent directly to you.
A piece of text describing the message you are replying to. Some mail
systems can use this information to correlate related pieces of mail.
Normally, you never need to think about this, because it is filled in
automatically when you reply to a message in Rmail (or any other mail
program built into Emacs).
The Message-Ids of previous related messages (a Message-Id is a unique
identifier generated when a message is sent). Like
‘In-reply-to’, this is normally set up automatically for you.
The ‘To’, ‘CC’, and ‘BCC’ fields can appear any number
of times, and each such header field can contain multiple addresses,
separated by commas. This way, you can specify any number of places
to send the message. These fields can also have continuation lines:
one or more lines starting with whitespace, following the starting
line of the field, are considered part of the field. Here's an
example of a ‘To’ field with a continuation line:
To: email@example.com, firstname.lastname@example.org,
The default contents of the ‘From’ header field are computed
from the variables user-full-name and user-mail-address.
On some operating systems, Emacs initializes these two variables using
environment variables (see General Variables). If this
information is unavailable or wrong, you can customize the variables
yourself (see Easy Customization).
The value of the variable mail-from-style specifies how to
format the address in the ‘From’ field:
Use just the address, as in ‘email@example.com’.
Use both address and full name, as in:
‘firstname.lastname@example.org (Elvis Parsley)’.
Use both address and full name, as in:
‘Elvis Parsley <email@example.com>’.
any other value
Use angles for most addresses. However, if the address must be
“quoted” to remain syntactically-valid under the angles
format but not under the parens format, use parens
instead. This is the default.
You can direct Emacs to insert certain default headers into the mail
buffer by setting the variable mail-default-headers to a
string. Then C-x m inserts this string into the message
headers. For example, here is how to add a ‘Reply-to’ and
‘FCC’ header to each message: