Hi there,
My name is Kristen Lee. I'm currently a freelancer, based in Australia, and have held a variety of B2b Marketing Manager roles. I've been conducting email campaigns for over 13 years and have consistently maintained delivery rates of 90% or more, with open rates around 20%.
During my career I've used Mailchimp (among others) very successfully which makes me wonder if there's more than the platform causing your problems. To really get a great outcome for you, the first step I would take is to do an assessment of why your emails are not being delivered. The possible reasons are many - for instance data quality, spam triggers in your content etc.
I can work on this initial step at an hourly rate of US$30 or negotiate a fixed price.
From there I would prepare a document of recommendations that you can choose to diy, or I can provide ongoing assistance with your email marketing.
If you would like to discuss further, please let me know.
Regards Kristen