Apple Mail - iCloud IMAP Connection Timing Out

For days I have been seeing the little warning icon next to my iCloud inbox in apple mail:

When I click on it I get the following message and it's the same every time:

I opened connection doctor and after some time this is what it showed for the iCloud IMAP Connection:

I'm not sure why this issue is suddenly occurring and it's quite frustrating.

I have checked system status and everything appears to be up and running.

Here are the things I have done to try and resolve the issue:

• Enable/Disable iCloud mail account
• Rebuilding the account with the rebuild option
• Restarting the computer
• Resetting SMC.

Nothing seems to be clearing this up and I'm about ready to just try reformatting the computer.

Does anyone have any ideas as to what may be causing this issue? I don't see an option to change the default IMAP server.