So my friend calls me up saying his emails arent working on his Mac any more so I think its probably something simple like a port number hes messed up, but I check with the guy who set up his website and even download the settings from the cpanel that sets up the account for you but I can not get the emails to work.
I didnt write down the exact error but it says something like can not find the IMAP server.
The Mail app was doing all kinds of strange things, I deleted 2 of his email accounts so I could recreate them but one of them kept reappearing, I click the "-" button for account 1 it goes, I click the "-" button for account 2 it goes and account 1 reappears, I click the "-" button for account 1 it goes, I close the window then I close Mail, reopen Mail and account 1 is back there again
Eventually i got rid of it by repeating until it went

Then I tried setting the account up in Outlook and it failed as well, said can not connect to the server. Outlook also said look at your DNS servers so i changed them to but no difference

Both accounts work fine on his iPhone and also on my Galaxy S7 when I tested it. They have worked on this Mac before but he has had problems at times.
It on OSX 10.11.6
Its Late 2012 iMac i5, 8GB, 1TB HDD

Any ideas what could be wrong?