[nos-bbs] JNOS 2.0 (and 1.11f) - smtp configuration notes

[maiko at pcs.mb.ca]

Hi all,

Well it took me long enough to figure this out, but here is
a slightly lengthy, but hopefully useful explanation of how JNOS
does mail delivery to the outside world.

I was forced to go through this exercise because I could not get
JNOS to deliver mail to any point past my ISP's subnet.

1) The 'smtp ga' option.

  Use a domain name and not an IP address. Many ISP now rotate their
  smtp servers on a regular basis. For example, 'smtp.a.b.com' could
  easily point to a different server every few times it gets resolved
  by JNOS for mail delivery. My isp rotates among mx1, mx2, mx3, etc,
  and it can get interesting how some ISPs do this stuff.

  For example, instead of using this :

    smtp ga 1.2.3.4

  Use a domain name instead, for example :

    smtp ga smtp.someisp.com

2) My ISP does NOT allow SMTP to leave their subnet. If I want to have
   mail delivered outside my ISP (to the rest of the world), I have no
   choice but to send it to the smtp server of my ISP.

   To FORCE JNOS to send mail to the 'smtp ga' entry, you MUST switch
   the 'smtp usemx' option OFF !!! In other words, make sure :

     smtp usemx off

   This causes ALL mail deliveries to go via the default gateway that
   you have specified in the 'smtp ga' command.

   Note : One possible issue with the above, is if my ISP does not like
   the 'HELO ve4klm.ampr.org' it sees coming from my box that itself
   actually resolves to my commerical ip address. Does not seem to be
   a problem for my ISP anyways, and if you look at the headers at the
   destination it shows coming FROM 've4klm.ampr.org', followed by
   the *real* domain name and ip address. Some destination mail
   filters may not like that, your success will probably vary.

   Hopefully the above paragraph makes sense to most of you. Sorry
   if it doesn't :-)

   IF I were to have 'smtp usemx on', then MOST (not all) of my emails
   will try and be delivered by JNOS using direct SMTP from my box to
   the end user. BUT - My ISP blocks outgoing SMTP past their border
   routers, so the mail will never get delivered.

   IF 'smtp usemx on' is being used, delivery will ONLY occur if there
   is no MX record found for the recipient's email address. Delivery in
   that case of course would be via the ISP default smtp gateway. This
   is not consistent, so I would not count on the 'usemx' option to be
   reliable in this case.

Summarizing what I do to ensure that JNOS can deliver outgoing mail. I
have the following entries defined in my autoexec.nos configuration :

   a) make sure I specify a domain name and not an ip address for
      the smtp server of my ISP, for example :

        smtp  ga  smtp.myisp.somewhere.com

   b) make sure that I do NOT use MX records, for example :

        smtp  usemx  off

I hope this is helpful to some. Comments and corrections welcome !

Maiko Langelaar / VE4KLM