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Re: New Issue: NOOP clarification

2007-11-29 22:26:28

Glenn Anderson wrote:

I have definitely encountered what appeared to be a proxy that returned 421 and closed the connection when it encountered things it didn't like.

I wouldn't be surprise.

If I recall correctly, the proxy in question was returning 421 in response to a MAIL FROM command with an address that didn't pass some sort of validation it was doing, so this problem isn't limited to NOOP commands.

Good point, let me do a quick google here....

Ok, I searched:  SMTP proxy "421 5.5.2"

Very interesting! This seems this is an issue with the Microsoft Internet Security and Acceleration (ISA) server. MS has this KB description and resolution for it:

It was definitely following RFC 821!!  From the article:

    Note There is no Requests for Comments (RFC) that specifies
    the default size of the NOOP command. The command is 6 bytes
    by default (N + O + O + P + CR + LF).

    For more information, see RFC 821, "Simple Mail Transfer
    Protocol" and RFC 2821, "Simple Mail Transfer Protocol." To
    see these RFCs, visit the following Web site:

Go Figure!!

I hope there is some MS engineers lurking around here so they can at least the default setting for the length in the ISA NOOP filter. :-)


Hector Santos, CTO