Here an explanation for those who have no clue about SMTP:
Mail Client ------> My Mail Provider ------> Recipient's Mail Provider
SMTP SMTP
The "Mail Client" usually uses a dial up IP address. This is often an IP
address which is on a Black List. Therefore the "Recipient's Mail
Provider" would not accept it directly. The "Mail Client" therefore
sends the mail to the "My Mail Provider". This host can authentificate
the mail: the mail must be from the domain the "My Mail Provider"
administrates and the E-Mail address must exist. A spammer cannot use
"My Mail Provider" as an open relay because he has not a valid account
on this server. The "My Mail Provider" sends the mail to "Recipient's
Mail Provider". The "Recipient's Mail Provider" accepts the mail
because
the "My Mail Provider" has a fixed IP address and this IP address is not
an a Black List.
For those who still do not understand why it is not a good idea for
Coditel to relay their customer's non xyz(a)coditel.lu addresses, here's
the explanation:
Unlike "My Mail Provider" Coditels relay could not ensure that I did not
fake my From field. Infact I could even use a non existent address (as
long the domain exists in the DNS). Coditel would essentially be an open
relay reserved for their own customers. The From field could be anything
a worm would find in a address database, Coditel's mail server could not
filter it.
Everybody understands?
I mean if you understand the SMTP protocol and the fact I do not want to
change my own E-Mail address everytime I change a dialup service, than
you will see that I use my dialup access in a *sensible* way.
And yes: The engineless car is waiting for you ;-))))))
Patrick Kaell