According to the MU website all Early Action applicants will find out if they were accepted by February 1.
http://miamioh.edu/admission/high-school/application/deadlines/index.html
For my son, he received an email message telling him to go to the Miami Application Status Check website for an update. He logged in to find a brief acceptance note with a link to the Class of 2019 facebook page and the 2019 acceptance website (http://miamioh.edu/admission/accepted/). Less than a week later the acceptance packet came via snail mail.
Miami uses the hashtag #miamioh2019 for this year’s class to post to twitter and instagram. Looking back at the #miamioh2018 posts, Early Action students not accepted in December learned their decisions the first week of February.