Archive for May, 2009

Sitting behind a dynamic IP means that your going to get blocked by a lot of SMTP servers if you send directly from that IP address. Most ISPs allow their SMTP servers to be used as relay Smart Hosts; so when you send an email out to the internet it will relay to your ISPs SMTP server and then send from there…from that IP address.

Its a pretty simple thing to set up in Exchange System Manager:

1. In Connectors, right-click on Internet Mail SMTP Connector and choose Properties.
2. Change the radio buttons to: Forward all mail through this connector to the following smart hosts
3. Enter your ISPs SMTP server in here, if you have the IP be sure to enter it within square brackets, below is the address for iiNet in Australia.

1. All SMTP servers these days require authentication to send outbound through them, so select the Advanced tab.
2. Then click Outbound Security
3. Choose Basic authentication
4. Click Modify
5. Enter your ISP user name and password and click OK

The Exchange server is now setup to relay outbound mail through your ISP, so that should see all your mail successfully arrive at it’s destination 100% of the time. But be sure to test it out and check that your ISP allows the use of a Smart Host.

For inbound email I have also now added a 2nd MX record for my domains which points to my web server (which is how I used to have email set up), which means I will have another layer of redundancy for inbound emails, should I lose my ISP connection for the server or it crashes etc.

Now time to kick back and wait for the emails to flood in, though not SPAM anymore!

So now that I have Exchange all hooked up and chugging away, I still had a few issues to sort out before I could (In Demtel’s Words) “Set it and Forget It!”. Namely, now that my domain’s MX records pointed straight to my server, there was no SPAM protection (when hosted on my web server, I had SPAM Assassin). On another SPAM related issue, because I am behind a dynamic IP, a lot of SPAM black lists block these ranges so I was getting a few bounce backs as a result of that… so I need to enable the exact same filtering that is blocking my outgoing emails currently!

So firstly, I setup my Exchange server to cross reference emails against a publicly available SPAM black list, SpamHaus. You do this via adding a connection filtering rule in message delivery properties (in the Exchange System Manager snap-in):

1. Under Global Settings, right-click Message Delivery and select Properties
2. Select the Connection Filtering tab
3. Click Add
4. Enter zen.spamhaus.org as the DNS Suffix of Provider and Display Name
5. Clock Ok

Next you have to manually enable filtering with this rule on your SMTP Virtual Server. To do this:

1. Under Servers > *Server Name* > Protocols > SMTP, right-click your SMTP server and select Properties
2. Click Advanced next to IP Address
3. Click Edit
4. Tick all the Check Boxes in this window and choose OK

So now that has blocked dynamic IP ranges and publicly known SPAM servers / address ranges for sending you email, too easy! As I don’t have that many address on my domains, this and some basic SCL filtering is thus far proving to be very effective at blocking SPAM. Obviously on an enterprise level you will need some 3rd party SPAM / Virus software on top of this basic SPAM protection available in Exchange.