title: Properly folding (wraping) header lines in email
body: <p>I have a PHP function to email subscriptions to users. I use the <code>BCC</code> so the users cannot see each other, and everything works great, with one exception: I worry about having too many emails per line such that the header line is too long.</p>
  
  <p>Note: I do break up the lists so that at most 75 emails addresses are used per email, but I don't want to go lower than that because of overhead.</p>
  
  <p>I have tried several ways to fold or wrap the line, but no matter what I do, any addresses after the first fold are ignored. What is the proper way to do this?</p>
  
  <p>I am interested in this for <code>TO</code> and <code>CC</code> fields as well.</p>