SMTP error 553, RFC 822, and Barracuda Spam Firewall

We recently had a strange issue where a script that creates and then emails a file to a user began failing.  It was strange in that the script had been in production for over two years, and there were no changes to the system on which it runs in that time.

In testing, we found that our Barracuda Spam Filter was refusing the mail with an SMTP 553 error code:

553 Requested action not taken: mailbox name not allowed

After some poking around, we found that the Barracuda’s firmware had been recently updated to v5.x, which includes a new option to enforce RFC 822 (ironic as the RFC is from 1982!).  The upshot seemed to be that email addresses (of both senders and recipients) need to be enclosed in angle brackets, or they are considered to be invalid addresses.

So if the email address is

user@example.com

Change to

<user@example.com>

Obviously, for scripting purposes, you’ll need to enclose the address in double quotes, and escape the quotes themselves.  Good times!