Adding the SSH keys on your github site is the simple solution. I am using 3 github sites; - 1 external - 2 behind the firewall
Each have their different email address for security reasons.
So, quite often, I get this error - if I mess up things. I was looking for a solution so that you can create a public rsa file for each github site.
The solution was to create
Host User git Port 22 Hostname github-site1.com IdentityFile ~/.ssh/github_site1_id_rsa TCPKeepAlive yes IdentitiesOnly yes Hostname github-site2.com IdentityFile ~/.ssh/github_site2_id_rsa Hostname github-site3.com IdentityFile ~/.ssh/github_site3_id_rsa
I am sure there are other better ways to solve this problem.
I would appreciate comments.