Setting environment variables in your crontab files, as in your example...
...is only supported in certain versions of cron. In particular, crond by Paul Vixie, which is typical on many Linux distributions, supports this syntax. It looks like Hardy may be using something else. Looking at the crontab(5) man page should give you more details on the syntax supported by your locally installed version of cron.
If you need to ensure that environment variables are set correctly, you can set them on the individual crontab command line, like this:
*/3 * * * * root env MAILTO= SHELL=/bin/bash /usr/local/sbin/bfd -q