ssmtp error - 451 See http://pobox.com/~djb/docs/smtplf.html

[kevin_i_orourke]

I recently updated ssmtp to 2.60.7 and since then I keep getting an error message in my logs:
[sSMTP] 451 See http://pobox.com/~djb/docs/smtplf.html.

I'm assuming it's happening when cron tries to email me the output of my daily cron jobs, seeing as the output never reaches the address its supposed to be going to.

From the description at the URL in the message it sounds like the problem might be more application-level (cron) than ssmtp-level, but this used to work fine until I updated ssmtp.

Any ideas?

Kevin.