What I forgot to add:
If Coditel would relay their customer's mail (maybe they even do it,
haven't tested it), then the other ISPs soon would have to put Coditel's
mail server to a Black List. At the moment they only have to do it for
Coditel's dialup address range! If Coditel's mail server only sends
Coditel addresses and my mail provider only sends my mails, it is enough
to have a Black List blocking all dialup address ranges to protect
against worms.
Now imagine servers like Coditel's mail server that are not on a Black
List relay mails generated by their customer's worms! Coditel cannot
check if the From: address is valid! Remember!
Yes, I do get emotional when somebody (who never has read a RFC document
about SMTP) says I would not use my dialup account correctly!
Patrick Kaell