sendmail configuring port numbers

Tue Oct 13 23:02:28 EDT 2009

On 10/13/09 17:34, quoth Ben Scott:
> On Tue, Oct 13, 2009 at 4:40 PM, Steven W. Orr <steveo at syslang.net> wrote:
>> The list manager running on "A" was configured to send to localhost:24 ...
> 
>   Why?  :)
> 
>> I did this by setting:
>> define(`confMAX_RCPTS_PER_MESSAGE', `20')dnl
>> which for me makes sense. (Am I wrong?) :-(
> 
>   Well, that means Sendmail will reject envelopes with more than 20
> recipients.  Which means you won't be able to send or receive messages
> with more than 20 recipients.  Since you later go on to complain about
> that limitation, I'm guessing it's wrong.  ;-)  Read on for more.
> 
>> * I want submit.mc to listen on port 25 and port 24 of localhost.
> 
>   I'm pretty sure you *don't* want that.
> 
>   Don't dick around with submit.mc unless you *really* know what
> you're doing.  Now, I myself don't really know what I'm doing when it
> comes to this aspect of Sendmail, so I've steered clear myself.  My
> limited understanding is:
> 
>   submit.mc builds submit.cf, which is used by Sendmail when running
> in MSP (Mail Submission Program).  MSP mode is used when
> /usr/bin/sendmail is invoked by local programs to submit mail into a
> mail queue.  It doesn't listen on any ports and doesn't run as an SMTP
> MTA.  It's part of a privilege separation mechanism and is basically a
> Sendmail internal.  Here there be dragons, etc.
> 
>> Am I trying to do something that is a good idea?
> 
>   Possibly not a good idea.
> 
>   All the SMTP standards -- RFC-821, RFC-2821, and RFC-5321 -- say you
> MUST accept a minimum of 100 recipients.  If you want to go ahead and
> reject on fewer, I don't know what will happen, but since you're
> technically violating the standard, beware of nasal demons.
> 
> http://tools.ietf.org/html/rfc5321#section-4.5.3.1.8
> 
>   I honestly don't know.  Sometimes standards get things wrong or lag
> behind reality.
> 
>> Can someone tell me how to do it if it is?
> 
>   I'll ignore the question of whether it's a good idea or not for
> purposes of discussion.  :)
> 
>   confMAX_RCPTS_PER_MESSAGE just defines the Sendmail option
> "MaxRecipientsPerMessage".
> 
>   I think the only way to have a multiple sets of Sendmail options is
> to run another instance of Sendmail.  That would involve, at a
> minimum, another config file (.cf) and another queue directory.
> Presumably another macro config file (.mc) to build the config file.
> Possibly another MSP to go with it, which would also be another set of
> files and another config file.
> 
>   Keep in mind that I'm far from a Sendmail expert.  There may be a
> more efficient way to do this, e.g., some way to apply
> MaxRecipientsPerMessage to a DaemonPortOptions instance, rather than a
> whole 'nother Sendmail instance.  But I don't know of one.
> 
> -- Ben

The way I understand it, sendmail made to switchover a while back to separate
out the sendmail process from the MSP. I guess the question is: Why did they
do this in the first place? I'm running a small home server. In total, it's
me, my wife, a few close friends and some aliases that mostly point to some
mailinglists. I will on occasion want to send email out to about 100 people,
and when I do, trust me, it's not about passing on the latest joke from AOL.
Frankly, if anything comes in with more than *5* recipients, the likelihood
that it's spam is about 99 44/100%.

The mailinglist manager that I use is something called majordomo2, not to be
confused with the majordomo of old. My /etc/services file says that there are
*three* ports for smtp.

lmtp            24/tcp                          # LMTP Mail Delivery
lmtp            24/udp                          # LMTP Mail Delivery
smtp            25/tcp          mail
smtp            25/udp          mail
submission      587/tcp         msa             # mail message submission
submission      587/udp         msa             # mail message submission

I'd really like to know what the intent is of these extra ports. Is lmtp
related to the sendmail MAILER(local)? Who is it that creates the listener on
localhost:25? Is it the MSP or is it the MTA? If it comes from the MSP then
shouldn't the listener on port 24 also come from the MSP?

Since I changed the value of MAX_RCPTS_PER_MESSAGE in sendmail.mc and I never
specified anything re Port 25 on localhost and I was stopped from sending out
mail to a lot of people, then it stands to reason that localhost:25 was
defined in sendmail.mc but if that's true then what does submit.mc actually do?

You are correct that I may be trying to play in the wrong nasal cavities, but
what I'd really like is to just understand how it works.

681 > telnet saturn.syslang.net 25
Trying 207.172.210.41...
Connected to saturn.syslang.net.
Escape character is '^]'.
220 saturn.syslang.net ESMTP Sendmail 8.14.3/8.14.3; Tue, 13 Oct 2009 23:01:02
-0400
^]
telnet> Connection closed.
682 >
*682 > telnet saturn.syslang.net 24
Trying 207.172.210.41...
telnet: connect to address 207.172.210.41: Connection refused
*683 > telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 saturn.syslang.net ESMTP Sendmail 8.14.3/8.14.3; Tue, 13 Oct 2009 23:01:16
-0400
^]
telnet> Connection closed.
*684 > telnet localhost 24
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 saturn.syslang.net ESMTP Sendmail 8.14.3/8.14.3; Tue, 13 Oct 2009 23:01:25
-0400
^]
telnet> Connection closed.
685 >

-- 
Time flies like the wind. Fruit flies like a banana. Stranger things have  .0.
happened but none stranger than this. Does your driver's license say Organ ..0
Donor?Black holes are where God divided by zero. Listen to me! We are all- 000
individuals! What if this weren't a hypothetical question?
steveo at syslang.net

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