Web Forms :: Sending Scheduled EMail From Web Application As External Service?

As indicated in the Subject, I have a web application (say APP) that should feature an e-Mail Notification Service (ENS). Activation of the Service is controlled by a Button in a dedicated page where some parameters are also included to set running Period (FromTime - ToTime), Interval, Recipients, etc.

When said button is clicked, it should maintain those parameters into database then launch ENS. Since ENS is expected to run for good according to set parameters, it logically should run as an external application/service, independent from APP.

When ENS starts, it needs to consult database to fetch parameters, then schedules its Timer to periodically check database for some transactions that when found, should trigger ENS to dispatch e-Mails to concerned Recipient(s).

CHALLENGES:

1. Launch ENS as an external application on button click from APP.Achieved by using System.Diagnostics.Process class. However, I encountered a problem in verifying if the process is already running before starting it. The root of the problem lies in
ProcessName property. Since ALL web applications must be launched via IE, hence, have
iexplore as their ProcessName, which is also applicable to all processes started through IE, it is very likely to have multiple processes utilising IE. How to check which is which? I couldn't figure out that.

Eventually, I ended up with a workaround: when the Process is started from APP, capture its ID and save it to database, then use this ID with GetProcessById() method for later verification. When the Process is terminated, reset stored ID in database.

2. What sort of application should ENS be: Windows Application or Web Application?

In either way however, ENS will always run invisible in the background being a Process. If this is the case, how about creating it as a Windows Service instead?

I did a lot of reading but still confused. However, the choice is limited now to either Web Application or Windows Service. Which one is more convenient to the task in hand?

3. What Timer to use?

I tried System.Timers.Timer in a test web application but it didn't fire! Then I used ASP AJAX Timer and it worked pretty well (I still need though to try running it from APP to judge its functionality). I came across some recommendations to use System.Threading.Timer but haven't tested that yet. Would it worth the trial?

4. ENS as a Windows Service.

If I create ENS as a Windows Service, would I be able to communicate with database? How would this influence the Timer to use?