Hi there
I hope you are doing well.
I have read out the job description...
Direct_mail plugin is even given the functionality which you have mentioned on job description.
You can easily send header , image , whysing editor text in the email newsletter.
I can build the system that kind which is fully backend managable and explain to you, so you can easily send monthly , weekely newsletter to the website users.
Looking forward from you !!
Best Regards,
Jimit Shah