title: Sending multiple emails - solutions used in large systems
body: <p>Previously I asked you about ways to test sending multiple emails at once.
  Now I would like to ask you about the solutions used in large systems - to send multiple emails at once.</p>
  
  <p>My question is somewhat complex:</p>
  
  <p>1) I'm very curious about solutions which are used now - I mean.. For example, in the banking system. Where sometimes it is necessary to send millions of emails. 
  How the bank-system send multiple emails to clients? </p>
  
  <p>2) Is that possible with simple gmail or hotmail account ? </p>
  
  <p>3) What is necessary to send very large amount of emails ?</p>
  
  <p>4) using "System.Net.Mail;" is a good solution? Sending one by one - to all bank clients? </p>
  
  <p>5) What should I do, to avoid sending emails as a spam? </p>
  
  <p>Thanks for help</p>
  
  <hr>
  
  <p>EDIT:</p>
  
  <p>I know that I can't prove it - but I don't need it for spam. Every large company computer system has to have a tool - which supports messages sending. </p>
  
  <p>It will be 100% legal! I want to create a tool - in configuration client will set his own email server (it could be gmail, hotmail or his own). And connect to his system - For example library or sth like that. 
  When school wants to inform all parents about the event or library.. or maybe something bigger - like a bank. </p>
  
  <p>I will send emails only for test - and I will use probably "Papercut" - but I don't know if it's credible tool.</p>
  
  <p>So, like I said - 
  I just want to know, how it is done in large systems - like bank-systems. </p>
  
  <p>and </p>
  
  <p>My solution for now is to get message and all emails from database and send them one by one, using "System.Net.Mai" - is that a good solution?</p>