[RFCI-Discuss] about FQDN for our smtp servers

[mouss]

Alex van den Bogaerdt wrote:
> On Tue, Apr 11, 2006 at 08:00:28PM +0200, mouss wrote:
>  
>   
>> This is debatable. The RFCs are self-contradictory here (one RFC 
>> requires clients to use a "canonical" name, but doesn't allow servers to 
>> check for that). of course, even requiring helo has been controversial 
>> for some time...
>>     
>
> This has come up here before.  Your statement is false in multiple ways.
>   
prove it. my "statement" above is comprised of two statements:
- RFCs are self-contradictory
- requiring helo has been controversial

your post doesn't adress any of these statements. you have just 
reformulated my post to be able to give your arguments.
> Indeed, >>something<< is not allowed by this RFC.  But people seem
> to think it means you cannot do >>anything<<.  That isn't right.
>
>   
I never said this. I didn't say you can't do anything. you can reject 
mail if the sender starts with a 'b'. people reject mail because the 
client IP is in some list. etc. That's not the issue here. please read 
before you reply.

> 1: It is most certainly allowed to verify the provided parameter.
> 2: One must not refuse to accept a message if the verification fails.
>   
but at the same time, it says the client SHOULD use a "canonical" helo. 
why should a client developer do any effort to follow this SHOULD if the 
same RFC says the server shouldn't refuse it because of that?

> In step 1 you gain some knowledge.  You cannot use this knowledge
> to refuse to accept the message.  This is what the RFCs forbid.
> The "MUST NOT" refers to a specific part of the RFC, not to anything
> you can come up with.
>
> The parameter must be a resolvable, fully qualified domain name
> FOR THE CLIENT HOST.  If this client host claims to be somebody
> I know it is not, using knowledge I possess, I can safely reject
> the message(s) in that session.
>   

and how do you get that knowledge? do you have a huge /etc/hosts on your 
machine?
> People claiming you cannot refuse messages based on HELO are
> RFC ignorant themselves.
>   

we are talking about the standard, not about what one can do if he 
wants. as said above, you can reject mail randomly (as far as you accept 
postmaster and abuse mail).