Emails not routed to Exchange server

You do not need to use NAT.

The best way to set the UTM and exchange up is:

Incoming mail: INTERNET > UTM SMTP Proxy > EXCHANGE
Outgoing mail: EXCHANGE > UTM SMTP Proxy > INTERNET

Remove you nat rule and ensure that your public DNS points to the UTM ip address or one of your additional ip addresses
Remove any smtp rule from outside as well. The only way you want mail entering and leaving your organisation is via the UTM. This will stop spam and also guard from the inside being compromised with a spam bot etc

Your Exchange server will also need a send connector configuring to send all mail to the UTM rather than directly out to the web

As an additional safeguard, make sure your DNS is configured right on the Exchange server (point it to the UTM) and the firewall rules are in place for dns on the UTM so that only the dns servers you specify can be used.

There is a really good guide on here called "rulz" by Bob & "UTM Tweaking guide v2" by Sascha in the general forum. There is also a few others about mail & DNS setups. Make sure to read those, it will be well worth it.

Hi,

Thanks for your answser.

I configured my UTM as described in article "Basic Exchange setup with SMTP Proxy" :

• Global : Simple mode 
• Routing : mydomain.be in Domains; and Exchange CAS in Host list
• Malware : Reject malware during SMTP transaction + single scan
• Antispam : Confirmed spam + 3 Advance features (Reject invalid HELO + Use BATV + SPF check)
• Data Protection : Scna within attachments and notify Administrator
• Exceptions : nothing
• Relaying : Upstream Hosts (the fixed IP of my router)  Is it correct ??
• Relaying : Allowed Hosts/Networks (my internal servers network + the fixed IP of my router) Is it correct or do I also need the DMZ interface ??
• Advanced : Use transparent mode + Allow SMTP traffic for liste host (Exchange CAS)
  

Now, I can see the mails (IN and OUT) coming and going to... SMTP Spool.

But, they remain stuck in SMTP Spool.

Outgoing message (from my Exchange to Gmail) :

Message Delivery Log:
2016-05-27 17:28:43 gmail-smtp-in.l.google.com [74.125.136.27]:25 No route to host
2016-05-27 17:28:46 alt1.gmail-smtp-in.l.google.com [74.125.68.27]:25 No route to host
2016-05-27 17:28:49 alt2.gmail-smtp-in.l.google.com [74.125.204.27]:25 No route to host
2016-05-27 17:28:52 alt3.gmail-smtp-in.l.google.com [173.194.72.27]:25 No route to host
2016-05-27 17:28:55 alt4.gmail-smtp-in.l.google.com [74.125.25.26]:25 No route to host
2016-05-27 17:28:55 myname@gmail.com R=dnslookup T=remote_smtp defer (113): No route to host

Incoming mail (from Gmail) :

Message Delivery Log:
2016-05-27 17:24:24 myname@mydomain.be R=static_route_hostlist T=static_smtp defer (-53): retry time not reached for any host

There is still something going wrong... but what ?

But the good new : the true SPAM mails are blocked (I can see it in SMTP log).

Delete the info out of the upstream host. You only use that if you have another email server upstream ie isp email server, smart server etc

Delete the info for the host base delaying. Add your exchange server into here.

Transparent mode - untick this & tick Allow smtp from hosts/net

I applied these configurations.

Still the same issue with incoming mails :

Message Delivery Log:
2016-05-27 20:36:30 myname@mydomain.be R=static_route_hostlist T=static_smtp defer (-53): retry time not reached for any host

But there is no trace of the outgoing mails in the logs.  And, of course, they are never received. 

Problems solved !!!   (I had a stupid static route).   [:$]