I know this is 3 weeks old but the reason that you can not send through Comcast e-mail server is because they are securing the server. Look in the customers e-mail settings in Outlook to get what you need. It is under Authentication and not all MFD's are capable of this.
POP Server: Requires SSL
SMTP Server: Requires POP before SMTP, port 465, and authentication of POP before SMTP or just authentication of just he name and password.
Hope this helps.