We have several AOL, Yahoo, and Hotmail test accounts that we use for monitoring delivery from our servers and have not had delivery problems. We do know that AOL, Yahoo, Hotmail, and other large email service providers sporadically drop emails and, in most cases, report to the sender's servers that the email was delivered. When they report that the email was delivered, it's in their hands to get it to you and there's not much that we or anyone else can do.
If your campaign to one of these addresses is not delivered, we would recommend trying to contact AOL, Yahoo, or Hotmail's customer support to find out why they did not deliver a campaign that you were expecting.
We also suggest asking your list member to put "m1e.net" as an "accepted sender" on their email filters since that is the server address used for email deliveries from our system.
Both Yahoo and Hotmail periodically experience delays in delivery that can sometimes last over a day. This is a common problem experienced by many email system administrators, not specific to email list management services like ours.