title: Meaningful interaction with IIS SMTP Server in .Net
body: <p>Our business sends a newsletter to a vast number of subscribers every week. When the business was very young, before I joined, they used a "free" version of some mass mailer that took six hours to send 5K mails and fell foul of every reverse DNS check on the internet.</p>
  
  <p>I upgraded this to a bespoke .Net widget that ran on the correct server and could send up to about 20k mails in half an hour with full DNS compliance. Unfortunately (or fortunately depending on your standpoint) our mail list has now outgrown this simple tool. In particular its lack of adequate throttling, it can make more mails than the server can comfortably send at once. I need to actually monitor how full the IIS SMTP server's available outgoing mail storage allocation is and throttle the load accordingly.</p>
  
  <p>Unfortunately I can find no information on where a mail object goes when (or even if) it is turned into a mail. I can implement a filesystemwatcher if I have a place to watch, currently I don't. If no actual mail file is ever created I guess I will have to create one to implement the functionality but I need to know where to put it. It would also be more reassuring to allow the system to confirm sending somehow but I have no idea how to go about retrieving data from the system that says a mail has been sent.</p>
  
  <p>Extensive Googling has proven vague on these points; so I was wondering if anyone here knew where I could get a guide to these problems, or could otherwise point me in the right direction.</p>
  
  <p>Many thanks.</p>
  
  <p>EDIT: In the end I gave up trying to measure throughput on the IIS SMTP server as a bad job. It just didn't seem to want to play. I'm now carrying out my logging in a separate location and just shunting it through to the SMTP server thereafter. I still don't know of anyone who really bothers trying to keep tabs on the doings of the IIS SMTP server and so this question as of this writing goes unanswered.</p>
  
  <p>Oh well...</p>