Hi
I have quite an experience with mailchimp. To get past the omnivore warning it all depends upon your e-mail list. Mailchimp lets you clean some of the problems in the e-mail list. But, using another bulk e-mail provider with better e-mail cleaning is preferred.
Again, it all depends on the list of e-mail list you have. Because in the past I used a paid account to clean list and even then Mailchimp couldnt get past the omnivore warning. So, I had to use another software.
Looking forward to chat more and in detail.