In MY software, the old method (PHPMailer)... the NEW method (some optimization outside of SwiftMailer too in all fairness) here are my results:
- HTML + text message with custom read/open tracking and link tacking - 100 people
- PHPMailer - 300 seconds
- SwiftMailer - 44 seconds
- Plain text e-mail with two 50KB attachments - 50 people
- PHPMailer - 229 seconds
- SwiftMailer - 56 seconds
