[X4U] mail still fried

[m senft]

Running a G5 2.0 DP with 10.4.1. Clicking "get new mail" in Mail
causes the accounts to instead go offline. Mail settings appear to be
the same as for the prior setup (an aged G4 with 10.3.9) except
initially, Mail on the G5 could receive but not send. I changed one
setting from requiring the password to not requiring it (but leaving
alone elsewhere) and it the became able to send but not receive. And
yes, I looked at all of Apple's help/support pages and nothing helps.
The ISP is Cablevision/Optimum Online.

Thanks,

     Mitchell