Mail - Triangle ! sign

I am getting a triangle ! sign next to my inbox and iCould in Mail. I do you mac mail and the cloud. I have logged on to iCould and everything looks good there. I logged into my Mail Preferences and again everything fine. The only way to get rid of this is to quit Mail and launch it again. If I click on the "Caution" sign this is the message on the pop up...

Alert

There may be a problem with the mail server or network. Verify the settings for account “iCloud” or try again.

The server returned the error: Connections to the server “p20-imap.mail.me.com” on the default ports timed out.

What is going on and how can I fix this?