It should be easy to attach, say, every file in a directory to a message using Mutt.
Googling, mashing keys, reading the fucking manual, etc.
(If you've re-bound any of the default keys, this may be wrong by a character or two.)
After you hit
a to attach a file, you can begin to
type a path (for local files), or press
? to get a
list of mail directories. Once you have typed part of the path, you
can hit tab to get a list of possible completions. There's no
mention of it, but you can tag files in this list with
Use these tags to attach the files you want. You can't type a
wildcard and have it automatically attach matching files, but if you
do type a wildcard, Mutt will filter the list and only show you the
files whose names match the wildcard pattern. You can then tag them
all by mashing
t real seriously.