You can define mail aliases, which are short mnemonic names
that stand for one or more mailing addresses. By default, mail
aliases are defined in the file ~/.mailrc. You can specify a
different file name to use, by setting the variable
mail-personal-alias-file.
To define an alias in ~/.mailrc, write a line like this:
alias nick fulladdresses
This means that nick should expand into fulladdresses,
where fulladdresses can be either a single address, or multiple
addresses separated with spaces. For instance, to make maingnu
stand for gnu@gnu.org plus a local address of your own, put in
this line:
alias maingnu gnu@gnu.org local-gnu
If an address contains a space, quote the whole address with a pair of double quotes, like this:
alias jsmith "John Q. Smith <none@example.com>"
Note that you need not include double quotes around individual parts of the address, such as the person’s full name. Emacs puts them in if they are needed. For instance, it inserts the above address as ‘"John Q. Smith" <none@example.com>’.
After editing the ~/.mailrc file, or if the file was modified
outside of Emacs, you can update the mail aliases used by a running
Emacs session with M-x rebuild-mail-abbrevs RET. This
prompts for the name of the file to use, the default being the value
of mail-personal-alias-file. A similar command
merge-mail-abbrevs prompts for a file with mail aliases, then
merges the aliases in that file with the existing ones.
Alternatively, you can use Emacs commands to define mail aliases.
The command define-mail-abbrev prompts for the alias and the
full address, and defines the alias to expand to the full address.
Emacs will save the added aliases whenever it offers to save all
files (for C-x s or C-x C-c), like it does with other
abbrevs (see Saving Abbrevs).
Emacs also recognizes include commands in ~/.mailrc. They look like this:
source filename
The ~/.mailrc file is not unique to Emacs; many other mail-reading programs use it for mail aliases, and it can contain various other commands. However, Emacs ignores everything except alias definitions and include commands.
Mail aliases expand as abbrevs—that is to say, as soon as you type a word-separator character after an alias (see Abbrevs). This expansion takes place only within the ‘To’, ‘From’, ‘CC’, ‘BCC’, and ‘Reply-To’ header fields (plus their ‘Resent-’ variants); it does not take place in other header fields, such as ‘Subject’.
You can also insert an aliased address directly, using the command M-x mail-abbrev-insert-alias. This reads an alias name, with completion, and inserts its definition at point.
The command mail-abbrev-complete-alias completes on the mail
alias preceding point.