Import tasks and activities ....PLEASE HELP

We are trying to import tasks using Data Administration Tools and have them assigned to the correct user. The problem here is that according to your help it says we must make sure the task is assigned to a user with the correct Zoho CRM ID and we are doing this correctly on our import file but the tasks all get assigned to me and no one else, this rule does not seem to be working.

The only issue I can think of here is that our Zoho CRM ID's are email addresses as they are unique and maybe your system does not the @ sign or other characters.

Can you advise whether this is a know issue here? or what we could be doing wrong, thanks in advance.

SEAN.