MTA Routing

Question

I would like an email to go through the following route to get to remote mail server. I am running comms suite 5.
1. Outlook Express -> internal MTA -> either one of the mail relay (ext-MTA1 and ext-MTA2)
2. Webmail -> LMTP -> mail store -> either one of the mail relay (ext-MTA1 and ext-MTA2)
I have setup the MX records in my local DNS server to load balance between ext-MTA1 and ext-MTA2. However, in both cases the email is rejected on the first MTA it goes through. The email never reaches the mail relays.
Errors
1. 03-Jul-2007 14:59:04.75 tcp_local J 0 xxx@domain rfc822; yyy@internet-domain 550 5.7.1 Relaying not allowed: yyy@internet-domain
Which MTA does it attempt to relay the message? Nothing is written in the log.
2. The mail store is the first MTA in this case. A Delivery Notification: Delivery has failed is sent shortly after the mail is sent with the reason: Illegal host/domain name found.
I am in a simulated environment using a switch with VLANs. There is no link to the Internet yet. I plan to get the mail routing correct before attempting to connect to the Internet. The correct behaviour in both cases should be either ext-MTA1 or ext-MTA2 bounces back the message and NOT the first MTA.
Please correct me if I am wrong.
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Answer 1

Hi,
Webmail talks SMTP, not LMTP. It is better to justconsider webmail to be 'just another email client'
and thus use the same delivery path as (1) - there
are configutil options to specify the outgoing smtp
host (and port) for webmail. Ideally the stores
shouldn't even have SMTP enabled, send all the emails
via the internal MTA servers, which then send them
onto the stores.
Can you provide me the configutil options to specify
the outgoing smtp host for the webmail? Is the local
SMTP the default as it seems to do exactly what you
have described?service.http.smtphost & service.http.smtpport
This way you reduce your troubleshooting paths --none of this 'oh email is kinda broken' stuff
(because outlook can send but webmail can't or vice
versa). Also you get to expand all lists in the
internal MTA and reduce the number of systems to
check for delivered email etc. Plus you only use LMTP
delivery thus reducing load on the back-end servers.
Do you mean I do not need to configure MTA, just the
message store during initial runtime configuration?
How does the internal MTA deliver email to the
message store? Are you saying that LMTP work without
configuring the MTA?No thats not what I mean. The message store system needs an MTA - the store just stores the emails, the MTA is needed to deliver emails into the store. Email can be injected via either the LMTP daemon or the ims-ms (SMTP) daemon.
The traditional mail-server layout looks like this:
(internally destined emails e.g. [email protected])
Email client -> SMTP -> system 1 (internal MTA) -> LMTP -> system 2 (mail-store)
(externally destined emails e.g. [email protected])
Email client -> SMTP -> system 1 (internal MTA) -> system 3/4 ('external' MTAs) -> gmail or whatever non-organizational server
The internal MTA is a completely different install. Your original descriptions didn't make it clear whether 'internal MTA' was just the MTA associated with the mail-store or whether it was an 'internal MTA' within your organisation.
Here is a summary of the current observation. As you
may have noticed, the recipient is addressed outside
the local network. I create a zone in the local DNS
so that it won't give me the invalid host/domain
error.
All mails (webmail + outlook express) with invalid
host/domain seem to be going through the internal MTA
which then talks LMTP with the message store. The MTA
for the message store is active. However I do not
know if it is used at all. After switching to LMTP,
the system seems to be smart enough to favor LMTP.
After the mail reaches the message store, it simply
bounces back stating delivery failure. Is it normal?I think you have a fundamental knowledge gap with regards to how email routing and non-delivery notifications work. By operating in an environment which sounds like it doesn't have a workable DNS configuration is only making life even more difficult.
The email is most likely bouncing back because it can't be delivered, the MTA does an MX record for the invalid domain, can't resolve it, creates a bounce email and sends it back to the sender. You need to read the information in the bounce email very carefully - it should explain why you have the bounce email.
Mails with valid host/domain configured in the local
DNS is queued on the tcp_local channel of the
internal MTA.
Here are my questions:
1. I am very new to DNS. How do I configure the
internal MTA to relay the mail to external MTAs using
DNS MX records? The message store MTA seems to
deliver the email directly to the Internet. I do not
want this behavior.I already answered this. You add the 'daemon <external MTA MX address'> to the channel which handles 'external' emails, i.e. the tcp_local channel.
2. For external mail access, do you recommend
installing an external MTA local to webmail or just
use an external MTA on another host?This depends on how big your email load is, whether you want room for growth, whether you want to isolate of email routing vs. email storage and any number of factors.
Regards,
Shane.