If you are using Outlook and sending email through Street Context follow the steps below for configuring Outlook as your default mail client.
In the Start Menu search for control panel and double-click on Control Panel
Using the search bar located in the top-right corner, search for default programs. Then, double click on Default Programs.
Under Email, click the Mail icon.
Select your Outlook program from the list and make it your default choice.
Click on Associate a file type of protocol with a program.
Make sure Default apps is selected from the menu under Apps (left-hand side). Scroll all the way down and click on Choose default apps by protocol.
Scroll down in the list of protocols until you find a MAILTO entry. Then, double-click it to choose from multiple options.
Select your Outlook program from the pop-up menu.
And that's it! Outlook should now be configured as your default mail client.