Use a SMTP server, perhaps on the Exchange server where the Outlook client connects to send out emails to users.
And then use this tip for sending
Sending an Email in C# with or without attachments: generic routine.[
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Use your MySql to schedule when to send emails out and then use Windows Scheduler to run a program at intervals that you define.
When the program runs, it check with MySql to get all users that has to get an email.