Today I spooled up my first Azure instance, running Linux. Spent a few hours getting Apache, MySQL, Postfix, etc. configured.
Tried to send a test email from the web server to an account in our Office365 subscription. Messages are being rejected by Office365 with the message
550 5.7.1 Service unavailable; Client host [191.237.68.231] blocked using FBLW15; To request removal from this list please forward this message to delist@messaging.microsoft.com (in reply to RCPT TO command))
It appears that Microsoft Office365 has blacklisted all of the IP address space for Microsoft Azure.
I'm supposed to entrust mission-critical applications to Azure, when the guys running Microsoft's hosted Exchange services don't trust it enough to exchange mail with it?