L-R, I think you're confusing "stuff that microsoft produces" with actual Mail Transfer Agents.
All internet MTAs that I'm aware of would have no problems understanding and delivering those addresses. Sendmail, qmail, postfix, exim, smail, qsmtpd, etc etc.
I will stand firm on chastising anyone that narrows "valid email" down to their own limited view of email. Follow the RFC, or don't play at all. If you want to "embrace and extend", please do that in the privacy of your own cubicle, not out in public.
I will also stand firm on chastising those (such as you, L-R) who support such narrow views. Please don't do that. It makes my job harder as well.