Updates: Reason has been found here.
The Mail app started itself unexpectedly just now (2009-02-08 at 1:15 am). I remember this is the second time in 24 hours. Generally, if any mail application starts, it means a email link has been clicked to trigger it, or something strange behind the scene is using it. I did not set any account in Mail. The application just notifies me to setup one when it starts. Good side is nothing to lease out. Bad side is I'm not sure what is going on. So I put a note here to remind when it happens again. It is said that Mac OS X is a very safe operating system. I hope it's not a virus but a mis-clicking on email link by myself. - Update on 2009-02-13 at 0:00 The mail application started itself again. - Update on 2009-02-13 at 23:51 Started again. - Update on 2009-02-16 at 0:02 Again 2/13/09 12:00:03 AM Mail[1674] DeliveryAccounts are missing. Trying to restore from backup. (null) 2/13/09 11:50:02 PM Mail[686] DeliveryAccounts are missing. Trying to restore from backup. (null) 2/16/09 12:02:00 AM iCal Helper[328] CALScriptUtils error: send_mail_sbr /System/Library/Frameworks/CalendarStore.framework/Versions/A/Resources/iCal Helper.app/Contents/Resources/Scripts/Mail.scpt ( "Alarm - \U884C", "February 18, 2009 : \U884C", "username@maildomain.com", "" ) | { NSAppleScriptErrorAppName = Mail; NSAppleScriptErrorBriefMessage = "AppleEvent timed out."; NSAppleScriptErrorMessage = "Mail got an error: AppleEvent timed out."; }