I am having a similar problem , but I can not authenticate at all. What takes my attention is the fact that I actually can establish a connection. Here is the output of ssh:

user@user-laptop:~$ ssh user@myserver.org -p 80 -vvv
OpenSSH_4.7p1 Debian-8ubuntu1, OpenSSL 0.9.8g 19 Oct 2007
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to greendood.homelinux.org [X.Y.Z.56] port 80.
debug1: Connection established.
debug1: identity file /home/user/.ssh/identity type -1
debug3: Not a RSA1 key file /home/user/.ssh/id_rsa.
debug2: key_type_from_name: unknown key type ‘—–BEGIN’
debug3: key_read: missing keytype
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug2: key_type_from_name: unknown key type ‘—–END’
debug3: key_read: missing keytype
debug1: identity file /home/user/.ssh/id_rsa type 1
debug1: identity file /home/user/.ssh/id_dsa type -1
ssh_exchange_identification: Connection closed by remote host

If you have paid enough attention, you can come to the conclusion that I am trying to pierce some firewall (I am using port 80).
This command works in another network ,with a public IP, but not here, inside the firewall.
My question is, Could it be the reverse DNS issue? if this is the case, what is the correct option in sshd_config : “ReverseMappingCheck no” or “UseDNS no” ? Could it be another thing I’m missing about the firewall? (which I think is not the problem, ‘cos it actually can make the connection)

I have disabled password login, due to some attacs :p.

Any ideas?

Yes, but if you don’t have access to the sshd_config file, it doesn’t work too well.

Then you will notice your ssh connections go much faster. It is easier to comment out 2 lines in your ssh_config than to call your ISP, but whatever works for you