There are a few questions on here that come close to answering the questions but never really a definitive answer.
Is there a limit to Mailbox size, email count, and folder count in Outlook 2010 x64 where stability and performance will begin to be compromised? If so, is there documented information from Microsoft that my team can forward to users in our office?
I've had at least half a dozen users come to me with performance issues in Outlook and it's always due to mailbox size.
Here are the details of an .ost I'm looking at right now.
50+ Shared folders
~60,000 emails across the local Inbox, Sent Items, and Deleted Items.
another 30-40k or so emails across the shared folders
.ost total size is ~40GB
Most of our users are working with either Thinkpad T400's (being phased out) or Thinkpad T440p's and T450s' all running Win7 Enterprise x64.