I suggest you add Archive feature in Mac version exactly as in Windows version.
Archive feature in Windows cleanly allows storage of mail offline in a *.pst file. Archive functionality is missing in Mac Version. I carry 53 GB of mail with huge syncing and spinning issues.
Anko Staas commented
Archive feature as in Outlook for Windows is a necessity to have in have in Outlook for Mac as well. The size of of my e-mail is huge, earlier this week there was problem due to which my main profile had to be rebuild, which took 22 hours!