MailChimp.com long time customer had account limited when we emailed our customers, Internet

Our company has been using MailChimp for many years and never had a problem with them until recently.  

We hadn't sent a marketing campaign to one of our large customer lists in a long time, several months, and we decided it was time to send them an update.  The email went out without a problem, but then we started getting emails from MailChimp of "high abuse rate" and we were being suspended.  According to MailChimp anything over a 0.1% abuse rate (1 complaint out of 1000) is "high" and apparently a very small number of our customers did not want to receive our mailing list anymore and marked the email as abuse.  

Obviously it is impossible not to exceed 1 complaint out of 1000, out of thousands of customers receiving a marketing campaign there will always be a handful that click abuse or unsubscribe.  

We're currently seeking a new email marketing service.