* mu4e: update documentation

mu4e/mu4e.texi

@@ -454,7 +454,8 @@ As we have seen, we can do all of the mail retrieval @emph{outside} of
 @t{mu4e}. For that, set the variable @code{mu4e-get-mail-command} to the
 program or shell command you want to use for retrieving mail. You can then
 retrieve your e-mail using @kbd{M-x mu4e-update-mail-and-index}, or
-@kbd{C-S-u} in all @t{mu4e}-views.
+@kbd{C-S-u} in all @t{mu4e}-views; alternatively, you can use @kbd{C-c C-u},
+which may be more convenient if you use emacs in a terminal.
 
 If you don't have a specific command for getting mail, for example because you
 are running your own mail-server, you can set @code{mu4e-get-mail-command} to
@@ -527,6 +528,10 @@ For Gmail-over-@abbr{IMAP}, you could add the following to your settings:
 @end verbatim
 And that's it! We should now be ready to go.
 
+For more complex needs, @code{mu4e-sent-messages-behavior} can also be a
+a parameter-less function that returns one of the metioned symbols; see the
+built-in documentation for the variable.
+
 @node Running mu4e
 @section Running mu4e