Re: Back to Reverse DNS

Hello,

> We can't send email to the cellphones.  We get a response that it was
> undeliverable due to not being able to find cwemail.com.  This happens with
> the SNDDST command as well as from Outlook.  The outgoing mail server is
> mail.dilgardfoods.com.  It has been suggested to me this is a reverse DNS
> problem.

If you can't find cwemail.com, that wouldn't be reverse DNS...  that would
be forward DNS!  However, I *can* find cwemail.com, so I guess I don't
udnerstand.


> I called Verizon and they didn't understand how it worked at all for any
> destination in the above scenario.  They had me change Outlook to use
> outgoing.verizon.net as the outgoing mail server.  Then it works from
> Outlook.  This doesn't help the SNDDST command however.
>
> If I do CHGSMTPA MAILROUTER('outgoing.verizon.net') FIREWALL(*YES) then I
> get a rejection from cwemail (and other places as well) that they do not
> accept relayed email.  So I did a CHGSMTPA to set things back so at least we
> can send email to the rest of the world.

So, what you need is your own SMTP client that can have it's mail routing
configured independently of your iSeries SMTP server.  You could write a
program to do it...

However, that's not the way that e-mail is supposed to work.  You
shouldn't have to connect to a different host than the one the mail is
designed to be routed to -- that doesn't make any sense unless DNS is set
up incorrectly somewhere, or you've been given bad advice...

> I'm lost.  Is there some way to tell the iSeries to use something outside
> for outgoing mail without it being seen as relayed email?  It was suggested
> to me that I simply needed to talk to someone more knowledgeable at Verizon.

Normally the way that e-mail is routed is according to the MX records in
DNS.   At this point, I'm confused about what your e-mail addresses
actually are, and why you'd want them routed to verizon...

To send mail to johndoe@xxxxxxxxxxxx, you'd follow a pattern like this:

1) You compose the e-mail message in your mail-user-agent (MUA) which in
your examples was either SNDDST or Outlook.

2) The MUA sends the e-mail to an SMTP relay server that will queue the
message up and make sure it gets delivered.  This is generally a
machine that's always powered on, and always on the Internet, so it
can keep trying until the mail has been sent.  This is called a "mail
transport agent" or MTA.

3) The MTA decides where to send the mail via DNS.  It looks up the host
name and the MX records for that host name.  Then, based on the priority
numbers for the MX records, it sends the mail.

In the case of cwemail.com, I find the following:

   cwemail.com has address 66.39.23.180
   cwemail.com mail is handled (pri=10) by cwemail.tsimms.com

4) The SMTP server that receives the mail from the MTA in step 3 is also
an MTA, and depending on it's own configuration and the MX records that
point to it, it can either deliver the mail or queue it and pass it on to
yet another SMTP server.  This cycle repeats until one of the SMTP servers
decides that the message is for a local user and delivers it.

5) When delivering the mail, the MTA calls a program that is designed to
save the mail in the local mailbox format... this is the mail delivery
agent or MDA.

6) Once the message is in the mailbox, the user can read it with local
e-mail software, or more commonly nowadays, he can transfer his mailbox to
his local PC using either the POP3 or IMAP4 protocols...  but that's
really irrelevant to the problem at hand.

What it sounds like to me is that you want mail for "someuser@xxxxxxxxxxx"
to be routed to "outgoing.verizon.net" -- if that's the case, you either
need to have an MX record that points cwemail.com to outgoing.verizon.net,
or you need an SMTP server that uses outgoing.verizon.net as a smart-host
(which is what the MAILROUTER() FIREWALL(*YES) settings do)

However, this seems absolutely illogical to me.  Why would
outgoing.verizon.net be the correct destination for cwemail.com?
Shouldn't you be using a verizon.net e-mail address if you want it to go
that way?

Also, the name "outgoing.verizon.net" sounds like it's an outgoing SMTP
server.  In other words, it's designed to relay mail that's leaving
Verizon's network, rather than mail that's coming in.  That's purely an
assumption based on it's name, though.

And what does any of this have to do with reverse DNS?   A symptom of
incorrect reverse-DNS would be that the messages would be discarded as
spam.  Or in the extreme case, a "cannot relay mail" error... "Host Not
Found" or mail being routed to the wrong server are not related to reverse
dns at all.