I can't speak for Outlook's performance at the MTA level, but the user-facing parts break all sorts of expectations I have from twenty years of standards-compli

I can't speak for Outlook's performance at the MTA level, but the user-facing parts break all sorts of expectations I have from twenty years of standards-compliant email. For instance---just at the tip of a very large iceberg---they have invented a completely new way of representing name/email pairs in the header fields, with the list separator being the semicolon, the email delimiter being square brackets, and a few other things. If I have a list of email addresses from some other source, I have to reformat it just to use it in Outlook. I have to use Outlook Web Access at work (no alternatives), which is even worse than regular Outlook, and I'm keeping a list of all the ways its user-facing interface is broken. I left the list at work or I'd be able to rant for pages right now.