Have been using MC for about 6 months with no problems and about 3 weeks ago started running into delivery problems for AOL subscribers.
AOL servers are accepting the campaigns, reporting a successful delivery to MC but we are getting all kinds of complaints from subscribers and advertisers that they aren't receiving the campaigns.
MC is saying they are working on the problem and will keep us "in the loop". They are pretty quick to respond to tickets, unfortunately there is never any useful information in them and no ETA as to a corrected situation.
They started by saying it happens once in a while, and lighting rarely strikes twice. We have campaigns that go out 3 days per week and haven't had any excessive abuse reports. There have been delivery problems reported on at least half of the last dozen campaigns.
AOL will at times try a smart delivery from what I have read if a campaign is questionable, test deliver to subscribers and throttle the delivery to see how a percentage of the list reacts to the campaign. A few abuse reports and the rest of the emails will get bounced.
There are no forums specifically for MailChimp that I have found so if anyone has anything to contribute I would like to hear. Or even if there are forums that are more specific to a service problem like this, please let me know.