Sending mails automatically with global.asax

Question

Hi

Im using global.asax page in my project to call a function that sends mails based on some conditions in database. These mails should be sent on daily basis on specific time. Its working fine for some time duration like when i set the time of half an hour. But somehow its not working for long time duration like if i set time of 4 or 5 hrs later. Also when the server goes down should I restart or run global.asax page again? If I run the application on server the functionality runs(within limited time period). But I need if the application won't run the emails should be sent indicating the application was not accessed for that day.