Even the simple act of upgrading your mail client to the latest version can result in a situation where your desktop based anti-spam solution finds itself disabled.
Server based anti-spam solution avoids these problems completely. Because the anti-spam solution is applied at the server level, changing a user's mail client has no effect on functionality and no user is able to disable the vital anti-spam functionality even if they wanted to, let alone by mistake.
Desktop based anti-spam solutions are generally designed with a specific product in mind. Most solutions will support Microsoft Outlook and another handful of email clients. Furthermore, most of these solutions support a specific version of that client software. This means that, when you upgrade, you are likely to have to buy another anti-spam solution that supports your upgraded mail client.
When we talk about software intended for the home user market, as opposed to businesses, we generally think that the home version will be much cheaper. But this is not so for anti-spam solutions.
The reason for this is that email has a one-to-many relationship. Your organization has only one mail server, yet it has many users. Desktop based anti-spam solutions are priced to make them profitable per copy, since home users are only going to buy one copy.
If an organization is going to apply client side ant-spam solutions, it will also need to buy a copy for every single user on their network. However, server based anti-spam solutions are designed for multi-user environments and are generally priced lower per user than the purchase of multiple desktop-based solutions.
As we can see there are many reasons why you should choose a server based anti-spam solution for your organization, with very few exceptional cases. In this case at least, your correct choice is clear.
Emmanuel Carabott CISSP heads security research at GFI Software. He has over 12 years' experience in the security field and is a regular contributor to several websites and blogs.