Mail ‘send’ fails (receive OK) ever since installing a Docsis 3 cable modem

Installation of the modem (Zoom 5341J) yesterday was no-problem, and all works exactly as before on my Win7 (64bit) ... except Win Live Mail refuses to send any messages.  There were no software or configuration changes.  The error message is:

    The connection to the server has failed.

    Subject 'windows email test'
    Server: 'smtp.comcast.net'
    Windows Live Mail Error ID: 0x800CCC0E
    Protocol: SMTP
    Port: 25
    Secure(SSL): No
    Socket Error: 10013

Comcast is no help.