Changed mail accounts from Pop to IMAP and now don't receive mail
I was having issues with all of my devices trying to access my email account on the server at the same time so I just changed the accounts in my mac mail client on my iMac from Pop to IMAP. Ever since I made the change, I can't receive any new email (in any of the accounts) unless I either close Mail and then reopen or take the accounts offline and then back online. When I do either of those things, the messages come in. What did I miss when I was setting up them up with IMAP? I didn't have a problem getting any of the mail that was on my server account immediately after setting the accounts up. It's just now I'm not receiving the new mail. Sending is no problem.
iMac (27-inch Late 2009), OS X Mountain Lion (10.8.4)