I have not used Smartpill 3 and PhpMailer so I can't comment on this method.
Yes, you can make changes to SMTP setting using a script. FM does not support html emails (currently only plain text) you will need to use a plugin for html emails. 360Works ScriptMaster: Free FileMaker Modular Plugin
MBS Plugin can also send emails with multiple attachments, properly encoded text, HTML with optional inline graphics, SSL/TLS and a lot of options for proxies and authentication.
So option 2 doesn't work without plugins.
Option 1 then, is there a way to transfer the mail attachement file from the client to the server without a plugin?