Emails will send but not receive! Aaaargh!

I have a pop email which suddenly on Wednesday decided not to receive any further emails. However, by accident I found I could still send??! It claims an error code of -17897 is the reason. This is an account authentication issue yet I have checked, double checked and triple checked that the info is correct. Weirdly the same settings work without issue in Apple mail, pad and phone. Am using Outlook 2011 for Mac and still using Yosemite...have held off the upgrade for now. All help I have found is geared to other versions or PC based. Is this a known issue following any operating system updates I am not aware about?? Any advice appreciated...do not want to lose any email folders. Thanks!