I've followed the directions for configuring the MX records for my domain provider, 1 & 1, I got these directions from zoho's forum and the help pages.  However there is an additional step and information it's requiring that isn't given in the forums.  It's asking for IP address, see the image below:

When I change it to CNAME I don't get the option to add the MX records.  Also, I can't only add the MX records and without the ip addresses.  It throws and error and says I need to add an IP address.  Is this correct?  What are the IP addresses I should use in these fields?  Is there another way I can configure my subdomain in 1 & 1 to ensure I can receive emails?  Can you provide detailed instructions to me on how to do this?

Any help would be greatly appreciated.  Thanks very much!