Running vmailsend < file_name.txt on the terminal gives this error:
Checking vmail.db version... OK
Connecting to database
/var/lib/gems/2.2.0/gems/vmail-2.9.6/lib/vmail/database.rb:28:in `<top (required)>': uninitialized constant Vmail::VERSION (NameError)
from ...
...
I added
require_relative 'version'
at the top of database.db and now it seems to work.
version info:
vmail 2.9.6
ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-linux-gnu]
Ubuntu 14.04.4 LTS