hmm..
Here is what my FTP Server setup looks like:
Max. User: 10
Idle Time: 2
Port: 65505
Passive Mode: Ranges 65501-65504 (I've changed it from default just for testing, I've forwarded these ports on my router to the dns-323)
Report external IP in Passive Mode checked
External IP: 50.99.137.191
Client Language: Unicode
Flow Control: Unlimited
SSL/TLS: Unchecked