Email for mac with El Capitan

[#1]

I have installed latest OSX system software and I can no longer receive emails and the setup of account looks very different, unlike the instructions on plusnet site for previous versions of OSX. When I send a test from my work email it pings back with permanent fatal errors which concerns me as it was working fine before the upgrade.
Any ideas, it's driving me mad!
Thanks

[#2]

mod:note
removed superfluous poll.

[#3]

have a look at the iOS guide http://www.plus.net/support/email/setup/ios-setup.shtml as it points out that need to make sure that the SSL is switched off etc.