Re: I'd like to be able to recieve mail, but not send it out (re: sendmail)

I tried what you suggested, and I guess I am still not being clear enough:

The server is a mail server for various domains. For discussion, let say 
it is
a server for the domain: restaurants.com (even though it is not).

Then when someone sends an email to [email protected] my sendmail
should pick up the mail and put in /var/spool/mail/john (john being the unix
account name, and as appropriately mapped from the /etc/mail/virtusertable).

John should then be able to pickup his mail via POP3.

Now this server should only recieve mail for domains that it knows about,
and never send any mail to another machine (route,relay,no create new..etc).

When I followed your directions, and I tried to send an email to john 
(from a
completely different domain, my account on mtc.ca.gov), I recieved back:

   ----- The following addresses had permanent fatal errors -----
<[email protected]>
    (reason: 553 5.0.0 <[email protected]>... Sorry, this computer can not send mail. Local deliveries only.)
   ----- Transcript of session follows -----
.. while talking to restaurants.com.:

>>>>>> MAIL From:<[email protected]> SIZE=1407
>>>      
>>>
<<< 553 5.0.0 <[email protected]>... Sorry, this computer can not 
send mail. Local deliveries only. 501 5.6.0 Data format error

Again, I replaced all the text that contained smtp/esmtp (in the form: 
$#esmtp $@ [$2] $: $1 < @ [$2] > $3 no smarthost: send )
with
$#error $@ 5.1.2<tab>$: "553 Sorry, this computer can not send mail. 
Local deliveries only."

Any followup or other ideas?

Thanks,
Joel


Michael Schwager wrote:

>>> I take it you mean you only want to accept incoming mail.
>>
>>
>> Yep.
>
>
> Ok, I can see I wasn't clear either... :) The issue is, what is the 
> definition of "receive" and what is the definition of "send it out"? 
> In order to answer this question, you need to specify with greater 
> precision where the mail is coming from and where it may go to.
>
> For example, receive may mean "From the Internet to any host in our 
> domain." Or it may mean, "From any host anywhere to this host." The 
> latter could (or could not) include the Internet at large, or it could 
> include machines in your intranet.
>
>> The concept is really simple: no mail goes out of this machine, except
>> via POP3 - mail never originates from it.
>
>
> I think I understand now. Although again the terminology of "going 
> out" implies some SMTP-based communication, originating on the local 
> host; with POP3 clients we usually think of them as "picking up" the 
> mail.
> I don't mean to be anal (though I don't deny I am :), but rather I 
> want to say that proper definition of the problem could garner quicker 
> responses from your audience and a quicker reply.
>
> And- finally- in this case, I would suggest the question would be 
> worded like this:
> "I have a host that is a POP3 server. I would like it to receive 
> SMTP-based email, but I don't want it to be able to initiate an SMTP 
> conversation. Any attempt by a local POP3 or Internet user to send or 
> relay mail through this host should fail. In other words, I want 
> sendmail to be able to deliver locally and that's all."
>
> Now for the answers:
> For a quick-and-ugly hack, find every line in the sendmail.cf that 
> contains "$#esmtp" or "$#smtp". Replace everything after the "$#esmtp" 
> or "$#smtp" with this text:
> $#error<tab>$@ 5.1.2<tab>$: "553 Sorry, this computer can not send 
> mail. Local deliveries only."
>
> That should all be one line. Anytime you see <tab>, make it a real tab 
> character (1 character) rather than that 5 character string.
>
> For example, if you see this (this is all on one line and is an actual 
> line taken from an existing sendmail.cf; you should have a similar one):
> R$* < @ [ $+ ] : > $* $#esmtp $@ [$2] $: $1 < @ [$2] > $3 no 
> smarthost: send
>
> ...replace it with this:
>
> R$* < @ [ $+ ] : > $* $#error $@ 5.1.2<tab>$: "553 Sorry, this 
> computer can not send mail. Local deliveries only."
>
> ...and so on, throughout the entire file. Then restart sendmail.
>
>> Isn't there a preprocessor variable that can be adjusted, instead of
>> editing the sendmail.cf directly?
>
>
> Not for the above hack, but that's the simplest thing I can think of; 
> I can't think of any circumstance that would allow a mail to squeak by.
> If you wanted to do it the legal way, you would probably need to write 
> some rules that end up in ParseLocal... it may be as simple as
>
> R$* < @ $+ > $+ <tab>$#error $@ 5.1.2<tab>$: "553 Sorry, blah blah"
>
> ...because you only want to allow local deliveries. What this 
> statement says is that: "By the time you get to this rule in ruleset 
> 0, if we haven't delivered it yet, and if it still has a hostname in 
> the email address- that is, if it's not a local recipient, then it 
> must be destined for a user on a host which is not this host. So 
> return it as an error."
>
> If that's what you want then you can use that rule, but test it first!
>
> I forget how to include ParseLocal via the preprocessor but I don't 
> think it's too hard.
>
>> Are there other smtp type programs that simply receive mail and never
>> forward, relay or allow sending of anykind?
>
>
> What you want is an MTA that only does local deliveries and I can't 
> think of any.
>
> -- 
> -Mike Schwager "btw the people who make open source software
> [email protected] generally don't have much sympathy for users"
> (Dave Winer)
>
>
>
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