It can be a temporary problem so, first turn off your device. Then restart again after 15 minutes.
You may also require changing some of the settings of your Outlook account, disabling the option to check the account as shown in figure: http://slipstick.me/jing/test-acct.png
Also try following fixes:
-> Firstly, delete the email account for your note and check if it makes any difference. Then re-add the account and try again.
-> Uninstall the Norton application (if installed)
-> Check if the size of your inbox growing too large.
The possible cause for the problem can be that the email provider has limited access to the email account from more than one device at a time. Change the password of your mail account. Check if it helps.