title: What are All the Ways a Programmer Could use PHP to Send an Email?
body: <p>I'm looking for a list of built in PHP functions that a programmer could use to send an email.</p>
  
  <p>The obvious answer here is <code>mail()</code>, but I'm also looking for a list of functions someone might use to manually open a connection to an MTA, or spawn a process on the local machine which might in turn send an email using sendmail, postfix, etc.</p>
  
  <p>The context here is I want to scan a large, unknown codebase for code that's sending out email (because we already located a call to <code>mail()</code>, and that's not doing it)</p>