Outlook "classic" is an Exchange client first an email client second. [1] A lot of speed depends on corporate setup, so I'll skip that. But integration, end t

Outlook "classic" is an Exchange client first an email client second. [1] A lot of speed depends on corporate setup, so I'll skip that. But integration, end to end, over core groupware elements like emails, distribution lists, calendars, contacts, etc is something nothing else does as well in my experience - though 3rd party components differ in quality (both of the solutions and how they got deployed) I can mimic or even do better on personal scale but group level? Nothing comes close, if only because they end up connecting disparate data sources with disparate protocols and everything gets a slight case of Chinese whispers or desynchronization (sure, you can reliably send ICS files as invitations, but they don't synchronize, etc) [1] a particularly funny aspect of this is that Outlook and Exchange do not support HTML Email directly - they have to wrap it in RTF, despite there existing a MAPI datatype for HTML content - if you use it, the MAPI library literally crashes opening the mail store.