Thunderbird Issues.........

I keep getting this mesage from thunderbird..........

Thunderbird connects to the SMTP server, and the SMTP server responds. The status message at this stage is "Connecting..."
The message could not be sent because connecting to SMTP server server name failed. The server may be unavailable or is refusing SMTP connections. Please verify that your SMTP server setting is correct and try again, or else contact your network administrator.
or:


Yea i checked my SMTP server... its good.. and it was working today....

I changed back from verizon dsl to timer warner cable and I am still getting this message....

Is it my isp..... blocking me...

my ip has come up a spam ip from spamhaus..........

Anyone.. ?