I was having trouble because my Maximizer 9 from CRM was crashing whenever I attempted to send an Email from Maximizer.

If you are having the same problem, then try this;

Go to File > Preferences and click on the Email tab.

Click on the "Advanced..." button.

Check to make sure that the correct default Email program is selected.

In my case, it had somehow been changed from my regular program to a program that I did not even have installed on my computer. Switching it back to my regular program seems to have taken care of everything.