One of the most visible ways in which mu4e integrates with Emacs is through
the modeline See (emacs)Mode Line. The mu4e support for that is
handled through a minor-mode mu4e-modeline-mode, which is enabled by
default when mu4e is running.
To completely turn off the modeline support, set mu4e-modeline-support to
nil before starting mu4e.
mu4e shares information on the modeline in two ways:
The global indicators can be disabled by setting mu4e-modeline-show-global
to nil.
All of the bookmark items provide more details in their help-echo,
i.e., their tooltip.
The query parameters in the modeline start with the various query flags (such as
some representation of mu4e-search-threads, mu4e-search-full; the
help-echo (tool-tip) has the details.
The query parameters are followed by the query-string use for the headers-view.
By default, if the query string matches some bookmark, the name of that bookmark
is shown instead of the query it specifies. This can be changed by setting
mu4e-modeline-prefer-bookmark-name to nil.
The global modeline contains the results of some specific “favorite” bookmark
query from mu4e-bookmarks. By default, the first one in chosen,
but you may want to change that by using the :favorite property for a
particular query, e.g., as part of your mu4e-bookmarks:
;; Monitor the inbox folder in the modeline (:query "maildir:/inbox" :name "Inbox" :key ?i :favorite t)
The results of this query (the last time it was updated) is shown as some character or emoji (depending on mu4e-use-fancy-chars) and 2 or 3 numbers, just like what we saw in See Bookmarks and Maildirs, e.g.,
N:10(+5)/15
this means there are 10 unread messages, with 5 new messages since the baseline, and 15 messages in total matching the query.
You can customize the icon; see mu4e-modeline-all-clear, mu4e-modeline-all-read, mu4e-modeline-unread-items and mu4e-modeline-new-items.
Due to the way queries work, the modeline is not immediately updated when
you read messages; but going back to the main view (with M-x mu4e resets
the counts to latest known ones. When in the main-view, you can use
revert-buffer (g) to reset the counters explicitly.