What can I do to correct this?

The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'paulineransom@yahoo.com,paulineransom1@… Subject 'Re: Tired with your poor health?', Account: 'pop.justhemail.com', Server: 'mail.bellsouth.net', Protocol: SMTP, Server Response: '553 Invalid address syntax', Port: 25, Secure(SSL): No, Server Error: 553, Error Number: 0x800CCC79