Snagit requires a MAPI compliant email client for sending email, and Windows must be configured to use that email client for the default MAPI client.
This can be done using Internet Explorer by choosing Tools > Internet Options > Programs > Email, and set Email to your MAPI compliant mail program. For example, if you use Outlook as your default mail client you would select it from the drop down box for email.
Some email clients have options for setting the default MAPI client in the email application itself.
If it still does not work, check the WIN.INI file. In the [Mail] section create an entry MAPI=1. If you don't have a [Mail] section you can create one. It should look like this:
To edit the WIN.IN file, choose Start > Run > sysedit
If it still fails, search the help for your email client for MAPI and verify that it is MAPI compliant. Some email clients require that you configure them within the client to be the default MAPI email client.