An issue has come up where the TLS FTP server is working fine internally yet not from the outside.
Using FileZilla in debug mode 4 the out put is as follows
Response:220 Microsoft FTP Service
Response:234 AUTH command ok. Expecting TLS Negotiation.
This is a problem with most firewalls that do layer 7 packet sniffing. Luckily for us the Firewall had bypass rules that can be configured to allow the TCP traffic to the destination internal server without inspection. Test internally first and if all is good your problem lies in the firewall (untangle) where you can just by pass it. refer to your firewalls manual on how to by pass layer 7 detection for FTPs / FTPes on port 21 and you shall connect with no problem. I recommend Filezilla with debug mode 4 to know where you get stuck If you have issues, give us a call!