RE: Back to Reverse DNS -- MIDRANGE-L

> Correct.  I've been given so much advice I'm not sure where to go next.  I'm
> about ready to do a Supportline call.

Yeah, I can sympathize with you. I guess that's one of the downsides of a
public forum, lots of people jump in and give you guesses. If you're not
familiar with how SMTP and DNS work, it can be  difficult to distinguish
the useful bits of information from those that really don't fit your situation.

> I can't get past the idea it's just got to be something simple and stupid.
> Centennial told me when they receive email for a phone, they verify where it
> came from which is, I think, where the reverse DNS comes into play.

Okay, that makes sense.

> In iSeries navigator, when I go into DNS, it wants me to upgrade to a
> newer version that requires PASE.  I have resisted this because I don't
> know what I am doing in that arena.  The box is checked for reverse DNS
> mappings.

That won't help because it's Centennial's server that needs to see the
reverse lookup -- and in all likelihood, they're not using your iSeries as
their DNS server.

DNS gets delegated piece by piece based on the periods in the name.  When
you do a FORWARD lookup on example.dilgardfoods.com, the server first asks
the root server who handle's the "com" domain.  It then asks the authority
for .com who handles "dilgardfoods.com".  It then asks the authority for
dilgardfoods.com who handles "example.dilgardfoods.com"...  so it goes
from server to server until it finds the one DNS server that's registered
with all of the others as the master for example.dilgardfoods.com.

Reverse DNS works similarly...  if your IP address is 66.15.42.200, then
it does a lookup on "200.42.15.66.in-addr.arpa"  Which again involves
asking the root servers who handles ".arpa", then asking the .arpa
authority, who handles "in-addr.arpa" and then "66.in-addr.arpa" and then
"15.66.in-addr.arpa" etc.  In the end, it will be a DNS server at the
company that owns the IP address 66.15.42.200 that will return the result.
Assuming that Verizon is your ISP, then it's Verizon's server for that
domain that's returning the string "bdsl.66.15.42.200.gte.net".  To fix
reverse DNS, you must get Verizon to change that string to read
"mail.dilgardfoods.com"

You can change your reverse mappings on your iSeries all day long, but
unless the authority for "42.15.66.in-addr.arpa" has delegated your IP
address to your iSeries' DNS server, it won't help, since nobody will know
to look at your iSeries DNS server.

Once you get that fixed, it should no longer be necessary to send the mail
through outgoing.verizon.net -- because now your iSeries SMTP should be
trusted by Centennial's SMTP.

Does that make sense?

If you can't get Verizon to do reverse DNS for your mail server, there are
a few workarounds:

1) You could cheat and set up a DNS entry on your system for cwemail.com.
Lie to it and tell it that cwemail.com is an alias for
outgoing.verizon.net -- then e-mail for cwemail.com will automatically be
routed through outgoing.verizon.net.   It's an ugly hack, but it'd
probably work.

2) You could write a program to use in lieu of SNDDST that checks for
cwemail.com, and when that's the domain, connects to outgoing.verizon.net
to send it.  In any other situation, it could connect to your local SMTP
server and send it there.

Disgusting, but it'd work.