The first time you run mu, you need to initialize its store
(database). The default location for that is ~/.cache/mu/xapian, but
you can change this using the --muhome option, and remember to pass
that to the other commands as well. Alternatively, you can use an
environment variable MUHOME.
Assuming that your maildir is at ~/Maildir, we issue the following command:
$ mu init --maildir=~/Maildir
You can add some e-mail addresses, so mu recognizes them as yours:
$ mu init --maildir=~/Maildir --personal-address=jim@example.com \
--personal-address=bob@example.com
(An older synonym for --personal-address is --my-address, which is still
supported).
mu remembers the maildir and your addresses and uses them when indexing
messages. If you want to change them, you need to init once again.
The addresses may also be basic PCRE regular expressions, wrapped in slashes, for example:
$ mu init --maildir=~/Maildir '--personal-address=/foo-.*@example\.com/'
If you want to see the values for your message-store, you can use
mu info.
Note: unfortunately, PCRE regular expressions are not the same as Emacs regular
expressions. Very simple ones match, but e.g. (foo|bar) in PCRE syntax is
specified as \(foo\|bar\) in Emacs/mu4e.
The good news is that mu4e can do the conversion automatically; however for
this to work, users needs to install the pcre2el package (available in
MELPA), and ensure it is available in load-path when Emacs runs (a normal
package-installation takes care of this). After that, mu4e takes care of the
translation automatically.
It is possible to come up with complicated PCRE regular expressions that are not
translatable; if necessary, experiment with pcre2el to avoid this.