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IMC and Interoperability

The Internet mail market has many different protocols, and there have been questions about how well products in the market interoperate. Software interoperability is important to purchasers because they need to know if a client from one manufacturer will work with the server from a different manufacturer. IMC's members are committed to achieving high interoperability between their products.

It should be noted that interoperability means different things to different people. In some markets, interoperability means that all products have passed some external conformance test, usually against some "reference" software. This type of testing, however, usually doesn't bring much value to the customer because the tests are usually for a small subset of features that everyone who has paid for the testing can pass. Testing a product against reference software instead of competing products also leads to pairs of products that both pass the test but do not interoperate.

A Better Way To Test Interoperability

A different model, the one that IMC embraces, says that interoperability testing should be on as many relevant features as possible, and should be done between each pair of products. Instead of using a third-party testing lab, the products should be tested by their manufacturers against their competitors. We believe that there are many benefits to this type of interoperability testing:

What IMC Will Do

In the coming months, IMC will produce a series of interoperability charts for the products of IMC members. For client-server protocols like IMAP and POP, the charts will have the clients in the rows and the servers in the columns; for peer-to-peer protocols like SMTP and S/MIME, the rows and the columns will have the same products. At the intersection of a row and a column will be a cell with the list of features on which the two products interoperate. Clicking on the cell brings up a page that describes how to set up each of the two products to produce the interoperability claimed in the cell.

The list of features will be agreed on by the companies. This might be considered a bit risky, because the companies may tend to be too generous about the list, but there are many checks and balances. The two companies will usually be competitors, and thus not prone to lie positively about each other. Further, a customer (or a competitor of the two companies) can test the interoperability claim by following the instructions given.

The charts will be constantly revised to add new products, to add new features, and to correct mistakes that may appear in the charts. For instance, if two companies say they interoperate on a particular feature and someone tells IMC that they don't, the complaint will be forwarded to the companies and they'll be asked to explain the discrepancy. If it turns out they were too optimistic, or they do indeed interoperate but the instructions they gave were incorrect, the chart can easily be revised.

Creating these charts takes time (although probably less time than it takes to do conformance testing). The participants have to agree on which features should be tested and the meanings of the features. This can be contentious, because companies that have features that other companies do not would want their features listed. However, it is expected that IMC members can agree on a reasonable set of features to start the charts with. After that, the testing also takes time, although it does not have to be done face-to-face.

Note that the upcoming IMC interoperability chart is different than the existing chart of Internet mail features that are supported by IMC's members. The features chart is an easy guide for finding the companies that support a particular feature.

Please watch the IMC site for more information about the first interoperability charts, which you should expect in the early fall. If you have further questions or suggestions, please contact IMC's director, Paul Hoffman, at phoffman@imc.org.