Why is the file always empty when sending a text file (as an attachment or in the body of the letter, it doesn't matter) by cron?

Question

linux

If you execute the cron -
What is an empty letter coming in? What is an empty file in an attachment coming in this way. And if you just execute in the console, everything comes as it should, what is an attachment in the body of the letter. For reference -
mail -s "new list" mail@domen < list.txt
mpack -s "new list" list.txt mail@domen

# echo $SHELL
/bin/bash
# lsb_release -a
Distributor ID: Ubuntu
Description:    Ubuntu 12.04.4 LTS
Release:        12.04
Codename:       precise

Answer 1

Specify the full path to the list.txt file

Answer 2

First, everything is run from the cron from under sh.
Secondly, write full paths to files (and better - binaries too, or set $PATH explicitly).