After you have succeeded in Getting mail, we need to index the messages. That is - we need to scan the messages in the maildir and store the information about them in a special database. We can do that from mu4e – Main view, but the first time, it is a good idea to run it from the command line, which makes it easier to verify that everything works correctly.
Assuming that your maildir is at ~/Maildir, we issue the following command:
$ mu index --maildir=~/Maildir
This should scan your ~/Maildir17 and fill the database, and give progress information while doing so.
The indexing process may take a few minutes the first time you do it (for thousands of e-mails); afterwards it is much faster, since mu only scans messages that are new or have changed. Indexing is discussed in full detail in the mu-index man-page.
After the indexing process has finished, you can quickly test if everything worked, by trying some command-line searches, for example
$ mu find hello
which lists all messages that match hello. For more examples of searches, see Queries, or check the mu-find and mu-easy man pages. If all of this worked well, we are well on our way setting things up; the next step is to do some basic configuration for mu4e.
In most cases, you do not even need to provide the --maildir=~/Maildir since it is the default; see the mu-index man-page for details