Starting last month in north jersey, Cablevision has started to block ALL smtp (port 25) traffic.
If you use the sendmail feature you MUST set the outgoing mail server to (mail.optonline.net) and use a valid domain name in the from field.
I found this out the hard way and after looking in my email client logs I saw no reply's to any of my smtp traffic.
I call Cablevision about this and they told me they did this to stop spam.
The only thing that they did not do is tell there customers...
After the change the email functions works great. I get email alarts on my pager when I get calls.. Very cooool...