Request: Send email Notifications/Autoresponders every certain time frame.

Is there a way to automatically send an email every 15 days?

I'm referring to the first case

What you're looking for is a newsletter/mailing list service -- you would need to avail a 3rd party service for this, such as MailChimp or MadMimi.

However, like what my colleague said, this has been forwarded as a request ticket. It is now up to our higher ups to decide what to do with the request.