[SwellJoe]

But, if something comes into the mail server via SMTP, it's gonna be protected by the mail servers own defenses. Unless the MTA also has a similar vulnerability, it wouldn't be dangerous in the SMTP case. Right? Or are you saying just the PHP mail() function is similarly exploitable?

[DCoder]

The parent post said "only implementations using sendmail (ie. not mail() or SMTP) are affected".

From my reading of the code, "only implementations using mail() (ie. not sendmail or SMTP) are affected".