Give at least one real life Remote Mailboxes example

[Dan Jacobson]

At the bottom of (info "(mailutils) Remote Mailboxes")
please add an example:

Here are examples of how one can use remote mailboxes

$ mail.mailutils --file imaps://ralph%40example.org:myp...@mail.example.com
$ mail.mailutils --headers --file 
imaps://ralph%40example.org:myp...@mail.example.com/INBOX.Spam

One notes:

We use the --file option.
@ encoded in username as %40.
No trailing / in URI.