Madmimi Integration ?

I do custom work/integrations for a fee — contact me through my website if interested.

But if they have a webform then you should just be able to map the field names (<input id="something" name="youshouldcopythis" type="text"...). Or if they have an API then you can post similarly.

Seeing the following on their List Management feature makes me hopeful it’s just a simple webform:

Plant a Mad Mimi webform on your site, and watch your audience grow!