I am a newbie developer of iphone from last few months. I am uploading apps behalf of my clients.
So one of my client add my email id in his itunes connect account. I completed the procedures and successfully login into itunesconnect.apple.com and uploaded the app.

But now i have other client, who also wants me to upload his app.
I am giving him my email to add me in his team in itunes connect not in developer. I got invitation in developer.apple.com.
But now problem is when he add me as a user it gives error like this
"The email address you entered already belongs to an iTunes Connect account. To continue, enter a different email address."

So if it means that i have to give different user ids to different clients?? How can i use single email id for different client's teams.
Any suggestions on it. Please mind that i am facing problem in itunesconnect not in developer.

Thanks in advance.