mail says "this account already exists" but it's nowhere to find
Hi,
I'm using a MacBook Pro 2014 and recently did a fresh install (= wiped the SSD before installing) of El Capitan. When I wanted to set up my e-mail accounts in Mail it worked fine for the first one, but the other one gives me an "This account already exists."-message. I already checked System Preferences –> Internet Accounts but it's not listed there. I also removed the credentials for the account from my keychain, because I thought it might be an iCloud sync issue. Nothing helped so far.
Does anyone know how to fix this?
Luca
MacBook Pro (Retina, 13-inch, Mid 2014), OS X El Capitan (10.11)