Grzegorz Janoszka wrote:
On Wed, 7 Jul 2004, Sander Holthaus - Orange XL wrote:
Just a quick question. As was reading up on my RFC and came across RFC1123
which states that you MUST NOT reject bad HELO's? Is this behaviour and that
But some other RFC say that HELO MUST be a valid name :)
No, it's the same RFC, which says that it must be, BUT also says that you cannot block just based on it not being so.
Rejecting bad HELO's is very efficient way to reject spam and viruses/worms without even receiving and checking the whole mail (saving cpu and net).
It's also a very efficient way to block many typically-configured Excahnge servers that are not using intervening routers. In many NETBIOS-based workgroups and domains, only the short name is configured by default and used in HELO.
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