I have an application that uses microsoft access as the database. The application is to allow users to book appointments online. I would like to include an email reminder service so that an email is sent to the user 24 hours or so before their appointment. Not sure how I can implement this so any ideas would be great?

Thanks in advance

Well, you would have to run some type of task every 24 hours.

There are a variety of ways to do this...

You can setup a page that handles this service and use a cron job to call that page once every xx minutes and check the database for an upcoming event in the next 24 hours and if it finds a match, send the email.

You can setup a vb.net, c# console application to run on the computer on a schedule (via scheduled tasks) that performs a lookup in the DB and if a match is found, send the email.

You can write a program (console app) that runs all of the time as a service and just executes a method on a scheduled basis so you manage the routine within this program, not via an external scheduler.

You mentioned that your database is Access, but if it was an Enterprise version of MSSQL, you can schedule jobs to SQL procedures to search and if a match is found, send an email from SQL itself.

etc.., etc..

the key here is that you need something to happen repetitavely, check for the condition, if there is a match, perform the desired action.