Compuserve identifiers are in the form 12345,1234; however, you cannot include a comma in an Internet email address. Compuserve has designed it so you can replace the comma with a period for this purpose. Furthermore, you must be sure to include your domain as well, so a properly formatted Compuserve Internet email address is "firstname.lastname@example.org".
As mentioned above, Internet email addresses must all include a domain (the part following the @ symbol) and should not include commas, spaces, colons, semi-colons, brackets, parentheses, or other such delimiters. Generally this would only include alphanumerics, periods, the @ symbol, the underscore, and the hyphen. Be sure to leave off angle-brackets that may appear around your email address in your mail client. If you are unsure of your email address, a technical support representative at your Internet Service Provider will be able to tell you.