Re: regarding illegally formed address and commands

Jack De Winter <> Tue, 24 December 1996 07:26 UTC

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Date: Tue, 24 Dec 1996 01:41:37 -0500
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From: Jack De Winter <>
To: Ned Freed <>
Subject: Re: regarding illegally formed address and commands
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At 01:52 PM 12/23/96 -0800, Ned Freed wrote:
>> just out of curiousity, what do people do with
>> illegally formed commands?
>Depends both on the command as well as what's illegal about it. As another
>point, PMDF will reject a command when the command syntax itself, as
opposed to
>the arguments to the command, is illegal. When an argument is illegal it
>depends on what the argument is used for. In the case of a malformed address
>argument to a MAIL FROM command, for example, PMDF doesn't care since it
>essential in getting a message delivered, and experience has shown that
>rejecting such messages on the basis of a potential problem returning a
>nondelivery notification later is not what users want.
>PP, on the other hand, is much more picky about this sort of thing. I don't
>believe it will let an invalid argument to MAIL FROM through at all.

So the command is checked but not the parameters?  Is this healthy?
Are there reasons that the parameter is not checked?  I mean if it
gets the MAIL FROM address wrong, it cannot bounce the message back

>> I checked around with
>> a couple of implementations over the weekend, and
>> not one of them did anything seeming intelligent
>> if I entered the following lines:
>> MAIL FROM:<jack@jacks world%>
>>  or
>> RCPT TO:<jack@jacks world%>
>> No error returns or anything.  Both the '%' and the ' '
>> are illegal on the domain name side.
>However, the % is somewhat more problematic. As far as I know it is
>syntactically legal to have it in the domain part of an address. The fact
>there are no valid Internet domains that have a % character in them is a
>administrative issue, pure and simple -- as the DNS folks often point out,
>restriction of domain names to alphanumerics plus dashes is purely an
>administrative, not a technical, matter, since the DNS can in practice
>contain almost anything.

Um... actually, according to the RFC821 grammar (which we are all
bound to until 821bis is finished), the domain part of the address
itself is a series of parts, each separated by dots, with an
alphabetic at the front; alphas, numerics, and a dash in the middle;
and an alpha or numeric character at the end.

i.e. is legal, as is, but,, and
are illegal... according to 821 at least.

I guess I am looking at this group to tell me what I should be
doing with a malformed SMTP level address?  Should I accept it
and deal with it later?  Or return some error code (if so, which

Jack (just trying to follow the specs which are vague on this point)
Jack De Winter - Wildbear Consulting, Inc.
(519) 576-3873

Author of SLMail(95/NT) ( and other great products.