Sorry for the quick follow up on my own post - I was mistaken with the port scan.
It seems port 3260 is open, but there is no response to any Initiator.

With the MS Initiator I get "Authentication failed" and Starwind says that the port is not opened.

Ports found open on the DSS are:

80
111
139
199
389
443
445
2049
3260
6666-6668
10000
11211