[nos-bbs] smtp gateway control

[Bob Tenty]

Add the following command to your autoexec.nos: smtp batch off

smtp pipelining means: sending multiple commands without waiting for a response of the server.


smtp servers like postfix, etc. can handle that (RFC 1920) but postfix has by default a setting
that senses when a client sends commands to earlier or if it doesn't wait (ESMTP)
for information to see or the server supports pipelining or not.

This is to prevent spam.
You can turn it off in postfix if you want to.

I also don't like the behaviour of jnos with the "smtp gateway x.x.x.x" setting.
(I hate it)
It should always deliver to the smtp gateway without fuss and at the first try.

Your smtp server in linux shouldn't  try to deliver the mail over Internet (ucsd.edu) to
deliver the mail to an ampr net address.

Maybe you made a mistake in the "ip rule" settings? 


73,

Bob VE3TOK



 


On 06/12/2011 12:34 AM, Michael Fox - N6MEF wrote:
> We’ve configured an e-mail gateway to allow packet users to send to 
> Internet email addresses. But JNOS has no way to control when the 
> gateway is used. We really need a way to control when the smtp gateway 
> is used (and not used).
> 
> Background:
> 
> JNOS can talk SMTP just fine with other JNOS systems. But it evidently 
> does not adhere to the current protocol very well which makes it 
> problematic when talking with non-JNOS SMTP mailers. For example, I get 
> this message in the log ever time JNOS connects to a current SMTP mailer:
> 
> Dec 5 20:58:31 cpk postfix/smtpd[10138]: improper command pipelining 
> after HELO from w6xsc-4.ampr.org[44.4.50.4]
> 
> Another problem with the JNOS SMTP server is a complete lack of security 
> mechanisms, such as checks, filters, etc. which are part of any typical 
> internet mail gateway. This isn’t a complaint, just a fact.
> 
> Scenario:
> 
> I’d like to allow JNOS to talk directly to any machine in my domain.txt, 
> and any machine with either a 44.x address or an ampr.org domain name. 
> Anything else should go to the smtp gateway for handling.
> 
> Problem:
> 
> The “smtp gateway” command is described in the manual as:
> 
> Displays or sets the host to be used as a “smart” mail relay. Any mail 
> sent to a host not in the domain.txt file or not found via a nameserver 
> query, will instead be sent to the gateway for forwarding.
> 
> The problem with this is that JNOS does a DNS query for any mail 
> destination that is not in domain.txt. We can turn off MX queries (with 
> smtp usemx no) but JNOS still performs an A record query. When it 
> receives the answer, it attempts to connect directly to the remote host. 
> With “smtp usemx yes” it will attempt to connect directly to the MX for 
> the remote host. So there’s no way to control when JNOS uses the smtp 
> gateway. In fact, as long as DNS is configured, and you’re sending to a 
> proper internet email address, JNOS will NEVER use the gateway since it 
> will always get an answer from the nameserver. That’s just not right.
> 
> Workaround:
> 
> I currently have iptables set to disallow SMTP connections on the 
> JNOS-to-Linux tunnel that are from JNOS to anything other than the SMTP 
> gateway. This means that JNOS will try over and over, but will be 
> unsuccessful in contacting the remote host. It will then try to send to 
> the gateway.
> 
> However, this workaround has a problem. Since it relies on a connection 
> failure, it can end up being used unintentionally, such as when the 
> remote system is another JNOS system. If that remote system is down 
> temporarily, JNOS tries and fails to connect, so it ships it to the 
> gateway. The gateway then tries to deliver it via the internet (out to 
> the internet, back in via the UCSD gateway, etc.) which is not allowed 
> on many JNOS systems.
> 
> Solution:
> 
> What we really need is a way to tell JNOS when and when not to use the 
> “smtp gateway”. I think the easiest approach would be to define when 
> JNOS should attempt a direct connect and then let the SMTP gateway 
> handle anything else. It seems that the best approach would be to allow 
> either IP address or domain name nomenclature. Here’s one example:
> 
> smtp direct local # host is in domain.txt
> 
> smtp direct address 44.0.0.0/8
> 
> smtp direct domain ampr.org
> 
> Instead of “direct”, something like “nogateway” could be used.
> 
> This basically says, if the host is in domain.txt or it has an address 
> of 44.x or it has a domain of ampr.org, then send it direct. Otherwise, 
> use the gateway.
> 
> Is this doable?
> 
> Michael
> 
> 
> 
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