It always amazes me when one finds a security issue that looks like something that should never have happened in the first place.
This one was found earlier this year by Wietse Venema who first discovered the issue in Postfix.
He fixed the Postfix server quickly, however, he went further. He actually tested many other servers sending commands that bypass that very security measure and to his surprised he found out that Postfix wasn't the only system affected by the problem.
For those interested, all the details of the problem can be found on the Postfix website as CVE-2011-411.
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