Yes finally I have found someone with the same issue!
It's insane, nothing is working properly :/ Mail App is not working, even other mail clients like airmail won't work. Anything to do with icloud wont work either.
Found this in the Console:
04/03/2015 14:29:25.109 com.apple.iCloudHelper[7588]: AOSKit ERROR: Config request failed, url=https://setup.icloud.com/configurations/init, requestHeaders=
{
"Accept-Language" = "en-us";
"X-Mme-Client-Info" = "<MacBookPro11,3> <Mac OS X;10.10.3;14D87h> <com.apple.AOSKit/217>";
"X-Mme-Country" = IE;
"X-Mme-Device-Id" = "371501A5-B53D-5CA1-8443-XXXXXX";
"X-Mme-Nac-Version" = 11AXX;
"X-Mme-Setup-FCE048DE-F34F-4FAF-A6DD-XXXXXX" = true;
"X-Mme-Timezone" = CET;
},
error=Error Domain=kCFErrorDomainCFNetwork Code=-1001 "The request timed out." UserInfo=0x7ff6eXXXX {NSErrorFailingURLStringKey=https://setup.icloud.com/configurations/init, NSLocalizedDescription=The request timed out., NSErrorFailingURLKey=https://setup.icloud.com/configurations/init}, httpStatusCode=-1, responseHeaders=
(null)
This is making me go insane at the moment as I can't work properly without restarting the machine every time this occurs...
Anyone else experiencing the same/similar issues?