How can I use these modules together? Is it possible to use Mimemail, Mail System, and SMTP Authentication Support modules together?
Currently I am using Mimemail to send HTML-formatted messages; however, because of the configuration of my server, these e-mails are often being recognized as spam.  To reduce the chance that they will be recognized as spam, I want to use the SMTP Authentication Support module.
Yes. We can use the Mimemail + SMTP Authentication Support. Plz check the link http://drupal.org/node/1200142 and check the part : Alternative Approach: Mail System + SMTP + Mime Mail