In late October 2014, Microsoft released a new version of Mac Outlook called “Outlook for Mac for Office 365” (a.k.a. Outlook for Mac), slated to replace the aging Office 2011 app. It includes several features from the PC version that Mac users have been forced to go without, most specifically true push support for receiving email (instant email delivery).
The major caveat is that the new Outlook for Mac is only available for Office 365 commercial users and consumer subscribers. Commercial users can download the new version of Mac Outlook for free by logging into their Office 365 Portal, then clicking the gear icon and selecting Office 365 Settings->Software->Outlook for Mac. Office 365 consumer subscribers can similarly download the new version of Mac Outlook by going to their My Account page
Microsoft recommends removing Outlook 2011 before running the new Outlook for Mac, however during my testing I’ve found the two can run side-by-side, and Outlook for Mac does not replace or remove Outlook 2011.
Although a promising glimpse of the version of Outlook that will be shipping with Office for Mac 2015, at this point I’d recommend users stick with the tried and true Outlook 2011. Numerous bugs have surfaced with the new Outlook for Mac, including some pretty major ones for companies that have their Macs joined to AD. Here is Microsoft’s list of officially know issues… https://support.office.com/en-us/article/Known-issues-in-Outlook-for-Mac-for-Office-365-af547e5c-4310-4d41-9944-08b1e842ebe4