1) Got to Default Programs (in Windows control panel) and turn off Outlook as the default mail client
2) Same place, under "Non Microsoft, select "the Bat!" program as the default. It won't say default what, but select it.
3) Go into your "The Bat!" program, select the account you want to be the default by clicking on it. Then go to the Account tab for that account, go to Properties, then select the General tab. On that page, near the bottom, is the check box saying "This account is the default for Mailto: URLs. Check that box, click OK at the bottoem, and you are done.
Note: I say "go to the account you want " because I have 7 email accounts set up in The Bat!. If you just have one,
no problem!