Update: An update in the course of 2014 rendered this obsolete.
Exchange email, calendars and tasks work well enough with iOS devices (iPad and iPhone) but not OS X.
Google revealed the usual spread of despairing cries for help followed by suggestions of varying usefulness. A couple of top tips include the news that, when there is no field to enter your domain, you can specify your username as <domain>\<username>. This is apparently well-known to Windows system administrators (although why anyone would do that job voluntarily remains a mystery to me).
This did not solve the problem. Nor did confirming the port number and all the other settings which work on iOS.
It turns out that iOS devices use ActiveSync, which is not available for desktops. That means OS X must use Exchange Web Services.
If your mobile devices work fine with your Exchange accounts but your OS X computers do not, despite apparently using all the right settings, ask your Exchange administrator if EWS is configured and how.
Finally, I would like to take this opportunity to ask Microsoft’s public affairs team not to get in touch. Open, non-proprietary protocols are available and your dreadful software, which has brought untold low-level misery to millions, should use them.
I’ve not had any problem with this at all – in fact I’m mightily impressed by how Apple devices (and operating system) cope with what is a pretty ubiquitous piece of Microsoft software (which is not especially true of all PC clients).
Only two problems I’ve had have been that Outlook for Mac on Office 2011 refuses to let you ask for a ‘delivery’ or ‘read’ receipt – MS say this is because it’s a technology which doesn’t work and is out-dated – which seems odd because they’ve kept it on the web version of Office 365.
Second problem is that iPads use the ‘Light version’ of the Exchange Web App – which is a pain – but not too much though because you can always use the Apple native apps – which as we’ve said are pretty good – also on newer iPads there are now free MS Outlook Apps for use with Office 365 (and therefore for Exchange servers)
I imagine you had no problems because the Exchange server you connected to from OS X was enabled for EWS.