I have received a few e-mail messages from time to time that I cannot Track In CRM in CRM 4.0. When I do, I receive an error message stating the message is too big. This is interesting because even one word messages will produce this error, as long as it's from a specific sender. I've found that certain senders, only a few, but enough to be a problem, cause this problem. ANY message they send cannot be tracked in CRM.
Thanks to CRM MVP Michael Höhne who gave me the solution. It's simple. Just increase the size of the MessageID attribute on the Email entity. It defaults to 100. Michael suggested increasing it to 250. That worked for all the problem senders I had. However, other MVPs suggested perhaps an even larger was sometimes necessary.
Of additional interest is that in CRM 4.0 you can actually increase the size of an existing attribute. In CRM 3.0, although you could change the size of an attribute, increasing it did nothing. You could reduce it which would only reduce the size the form would allow you to enter. But it would not change the actual data size. This has been changed in CRM 4.0. A nice addition.