We've got a 12 core xeon, 24GB of ram 2012 server. We've recently migrated from exchange 2010 (which was on another server) to exchange 2013 which resides on our new 12 core server. Accessing the OWA on the exchange server is fine; it's very quick and responsive however accessing it via any other computer connect to the domain via a 1 gpbs connection and it'll take 10-15 seconds to load.

Also running slow is public calenders that people in my place need to access, again taking 10-15 seconds to access and can sometimes cause outlook to not respond.

Further to that we have phones that connect via the internet (of course) to the exchange so people can get work emails when they are out of the office. Guess what, this is also running slow. I've have search for many solutions and have tried changing outlook authentication methods but there is no change in speed. The old exchange 2010 server no longer exists but there was no problem before the migration. Has anyone got any suggestions? Thanks :)

Must also mention that server 2012 that exchange 2013 is installed on is also the DC.

Update: It would appear that any connection via https is slow. It took more than 15 mins for an outlook client to download 50MB of emails (outlook anywhere).