title: Sending "on behalf of" emails
body: <p>I have been received a lot of emails "on behalf on". For example, the AddThis plugin sending a email from "addThis.com on behalf of myfriend@gmail.com".</p>
  
  <p>How do I do this in C#/ASP.NET? Also, does this work if we use gmail for our SMTP, albeit branded to our company domain?</p>
  
  <p>I'm also wondering if there are any concerns about this being unprofessional or getting flagged as spam on the client PC? In other words, have you guys actually implemented this...</p>