How do I stop iCal from launching Mail.app? I do not use Mail.app, instead using Postbox 2 for all my email needs. I do use iCal for my calendaring, syncing it with my Google Apps accounts.

Whenever iCal wants to send a reminder, it tries to open Mail.app to do so, which is highly annoying.

Currently the only solution I have working is to zip up Mail.app in /Applications so iCal can no longer access it. However whenever the OS updates (i.e. from Snow Leopard to Lion) it replaces Mail.app and I have to do this again. This seems overly hackish.

Is there a way to force iCal to stop trying to open Mail.app without having to manually remove Mail.app?
The instructions below (posted here) did it for us as our permissions were, actually, on "Read Only" and the Mail.app was still launching. 

Note: If iCal still opens Mail.app for mailing an event after you have set Postbox as your default mail client:


Within the Finder, right-click on the iCal icon and then select Show Package Contents.
Navigate to the "Contents" folder, then the "Resources" folder. Right-click on the folder called "Scripts" and select Get Info.
Expand the Sharing &amp; Permissions box and click the Lock Icon in the lower right hand corner to unlock this setting. Change any permissions that are listed as "Read Only" to "Read &amp; Write."
Restart Postbox.


If more information is needed, check out a more detailed Postbox iCal Integration page for more options and troubleshooting tips.

Have a great day!