IIS FTP Not Working Remotely Windows Server 2012 R2

Passive FTP requires that the FTP server have ports opened to it from the external network. Azure VM's use NAT, and thus needs extra configuration in order to support passive FTP.

The (rough) checklist:

• Set the external VIP in the IIS FTP manager
• Set the port range to use (you might wanna show some moderation here - configuring thousands of ports are not necessary unless this is a very, very busy FTP server with lots of concurrent sessions)
• Configuring the VM firewall to allow the FTP traffic (remember the custom port range you defined in the previous step)
• Add the remote endpoints (the same port range as previous steps) in Azure to the VM so that the ports will be forwarded

Here is a blog post from Microsoft that guides you through it.