SSH error in connection to a new Domain

Question

I was already able to connect to the server via ssh properly. But recently after changing the server fixed-IP address and domain name, I cannot connect to the server by DNS name. Despite, I can ssh to the server with its IP address. The error of ssh with domain name is the following:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
The DSA host key for example.com has changed,
and the key for the corresponding IP address X.X.X.X
has a different value. This could either mean that
DNS SPOOFING is happening or the IP address for the host
and its host key have changed at the same time.
Offending key for IP in /home/.ssh/known_hosts:10
  remove with: ssh-keygen -f "/home/.ssh/known_hosts" -R X.X.X.X
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the DSA key sent by the remote host is
*:*:*:*:*:....
Please contact your system administrator.
Add correct host key in /home/.ssh/known_hosts to get rid of this message.
Offending DSA key in /home/.ssh/known_hosts:11
  remove with: ssh-keygen -f "/home/.ssh/known_hosts" -R example.com
DSA host key for example.com has changed and you have requested strict checking.
Host key verification failed.

Answer 1

The answer is in the question:

ssh-keygen -f "/home/.ssh/known_hosts" -R example.com

You will get more info on the first google hit for the big message. WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!

Answer 2

You should remove line 10 from your known_hosts because the system signalized you about the problem Offending key for IP in /home/.ssh/known_hosts:10