This plugin works fine for me. but still have few bugs which need to be solved.
first one, I enabled "user_manual_text_part" by edited the phplist config file. After this plugin installed, even I typed my own text message, the mail will output all the text in uploaded html template with my own text message to be the text version.
second one, I got the below message when I tried to send test mail to a email address more than 1 time,
Database error 1062 while doing query Duplicate entry '67-862f59f5249354252cee6d22e99faa95' for key 'PRIMARY'