How to add a contact to a specific list?

Why I cannot add contact to a specific contact list?

• I ve been adding contacts to a specific list and suddenly I cannot add another name. get the message "Something unexpected just happened. Contact Yahoo customer care if problem persists. Problem does persist, but looks like there is no yahoo customer care. If problem continues will have to cancel my email account. Any suggestions? Like phone number where I can call?

• Answer:

  I've run into this same problem today, and determined the cause to be that the email address I'm trying to add contains an underscore "_" in the text. I've tried this will two different email contacts both of which contain the underscore, and it fails every time. I can add other contacts with no problem. Seems to me Yahoo email has a problem with these underscores.