MS Small Business Server - Send Emails via DNS

Hello Experts

This is an Exchange email sending problem that has been plaguing me for a very long time, for many clients and I am now left with no option but to resolve it once and for all.

We have about 80 Small Business Servers that we manage and maintain for our clients.  The MS Server operating systems in question are SBS 2003, 2008 and 2011.

Our client base use a wide variety of Broadband providers in the UK and their SMTP relay services / policies are very varied.  About 30 of our clients use broadband providers that do not provide a free SMTP service as part of their broadband package and as a result, we are forced to either use a 3rd party provider or set the Server to route through DNS (only 3 or 4).  Clients routing through DNS get many bounce backs from ISPs stating they have been denied due to SPAM filter rules.

As I am sure you are all aware, most ISPs block emails to the clients that are sent from DNS because they are classed as SPAM.  The total bill for the 3rd party providers is beginning to increase and I need a free or cost affective solution.

Do I need to register the clients domain names with the ISPs or setup special A records to verify where the emails come from ?

Any help or guidance is greatly appreciated


Andrew BarringtonAsked:
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Will SzymkowskiSenior Solution ArchitectCommented:
If you are using internal DNS to route mail to the internet you will need the following...

A record =
MX record =

You will also need to register an external MX record for the external domain being used for mail, along with reverse DNS setup accordingly.

Andrew BarringtonAuthor Commented:
Thanks Will

All clients have an external MX record (via the web host's DNS) pointing to their broadband's static IP address which then resolves via the router to their SBS Server for incoming email delivery.


Simon Butler (Sembee)ConsultantCommented:
You need to get the ISPs to set a PTR record on the IP address to match the DNS record that points there. That is the main reason that you will get message rejects.
You could also look at putting SPF records on to the domains. That can help, if they are set correctly.

Not sure what you mean by this:

"As I am sure you are all aware, most ISPs block emails to the clients that are sent from DNS because they are classed as SPAM.  "

Most of the major providers will reject email that is sent directly if there is no PTR record in place, but that is all. It is perfectly possible to get email delivered directly on UK broadband, as I am doing it myself with all of my clients who have static addresses - even the BT ones where you have to email BT to get the PTR record set.

The other option would be to setup your own server to use as an outbound relay in a data centre. You can rent a server for about £50/month, put IIS SMTP on to it. Put on a basic SSL certificate and use authenticated relaying. Added bonus, you can also use it for inbound email to store messages if the client goes down for any reason.


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