Every day, we get mail from our readers. Occasionally, there is a letter we think would be better served in a monthly letters to the editor column. Normally, our editorial staff is not really equipped to answer questions better served by your favorite Domino consultant. But Senior Technical Editor Ron Herardian, an independent consultant and messaging expert, volunteered to help out. This month: How to configure multiple SMTP MTAs and use multiple DNS domains.

Setting up SMTP email without transiting via the hub server
My office is the largest office in a worldwide Lotus Notes domain and I want to set up my Notes server so we can send and receive SMTP email without going through our hub server in Belgium.

We are running version 4.5.4 of the Domino server and I have downloaded the MTA (Message Transfer Agent), but the overall Notes administrator in Belgium is saying that it's impossible to set MTA to work up on another server in the domain.

To start with, all I want to do is to set up the MTA so all non-Notes addressed emails (except faxes) go straight to the Internet as opposed to going in a rather circular route of:

London -> Internet -> Belgium -> Internet -> Recipient

Is this possible? If so, how can we do it?

Andy Owen (aowen@amrop.co.uk)
IT Manager, Whitehead Mann Group

Ron Responds
Multiple SMTP MTAs (that's Simple Message Transport Protocol Message Transfer Agents) can be implemented within a single Notes network, each running on a separate server. Based on my experience with Domino messaging customers, this is a common issue in large Domino messaging systems. However, before you implement additional MTAs there are several things to consider.

Conceptually, the fact that you route Notes mail between Domino servers, over the Internet, to and from the SMTP MTA is not relevant to the overall message routing topology -- unless there are capacity problems resulting in routing delays or high communications costs that would justify additional MTAs. A related issue is whether or not you have established a capacity planning framework for Domino messaging.

It is indeed possible to distribute multiple SMTP MTAs to different locations. It is also possible to use multiple DNS domains to route inbound SMTP messages to different sites around the world. Alternatively, an intelligent mail hub can route inbound Internet mail, based on the user ID, to different MTAs (or to various MTAs and gateways). This can be done using sendmail with custom rewriting rules (I recommend Sun's implementation on the SPARC platform) or by an LDAP-enabled implementation of SMTP such as Netscape Messaging Server, which can be synchronized with the Domino Name and Address Book using third party directory synchronization products such as WorldTalk and my own company's GSS LDAP Synchronizer.