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Introduction to Cluster Gateway

Load sharing - Multiple Locations - IP Sharing

The Mailtraq Cluster Gateway allows you to install several Mailtraqs on your network to share the load, and makes them appear as a single machine to other mail servers and email clients.

It automatically detects which users are configured on which Mailtraq, and routes mail and collection requests to them.

A Mailtraq Cluster Gateway can be installed in the place of a single existing mail server without any need to reconfigure email clients or MX records. It is therefore an ideal solution for managing scalability issues.

The Mailtraq Cluster Gateway is provided FREE for use with Mailtraq.



Typical usage scenarios:


If your Mailtraq is CPU-bound (ie it is not responding quickly enough to client requests), you can use the Cluster Gateway to share out the load amongst two or more Mailtraqs. This is most common when users are using IMAP rather than POP3, as IMAP places a much greater computational burden on the hardware.

This may be more cost-effective than upgrading the mail server.

Read more about this usage.

Multiple locations with the same domain (local stores / branch offices)

If you have a single domain shared by multiple physical locations, yet want the local resilience and autonomy of providing each location with their own Mailtraq, you can use a Cluster Gateway as the public-facing interface directing traffic to the appropriate locations. This makes it easy to handle situation where staff are re-assigned from one location to another, yet need to keep their email address.


Use the Gateway to provide automatic failover from one Mailtraq to another if the first one suffers a hardware outage.

Migrating to Mailtraq

Use the Gateway to allow a phased transition to Mailtraq from another mailserver. 


If you only have one public-facing IP address, but you wish to share it across multiple Mailtraqs each running a different domain.

Read more about this usage.

Operating System and hardware requirements

The Cluster Gateway will run on Windows XP Professional or on Windows Server operating systems. The main difference between the two is the number of simultaneous half-open sockets they allow. Under most conditions the XP Professional will be sufficient, but Windows Server has higher limits.

The Cluster Gateway does not normally store any data on disk, apart from its log files, so you do not need to provide dedicated disk storage.

For optimum performance you may want to have multiple network cards, with one interface for the inbound connections and one for the connections to the mail servers within the cluster.


There is no limit to the number of machines which can be clustered, however at extremes (clustering several hundred Mailtraq servers) the overhead of determining which server is managing which user may become noticeable.

You should expect to be able to have several hundred simultaneous connections active. The limiting factor will not be the Cluster Gateway software, but the underlying Windows socket system. Windows Server operating systems have higher limits than Windows XP


You need to have a suitable license for each Mailtraq machine – so if you have 1000 users split evenly over two machines, you will need two 500 user licenses.

You do not need a separate license for the Mailtraq Cluster Gateway – that is currently available at no charge if you have a Mailtraq license with current Upgrade Protection.


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