need someone to resolve omnivore issue when importing emails to the list -mailchimp account

I need to import 15,000 email address from excel sheet to mail chimp account, i've been getting the omnivore warning message, after importing the emails to the list. I've tried removing some emails, looking into the syntax of email address, nothing worked out, need some expert, to look into the list, and see if you can figure it out to resolve the issue.