[REBOL] Re: Sending e-mail using non-default server
From: holger::rebol::com at: 18-Nov-2001 15:29
On Mon, Nov 19, 2001 at 09:47:42AM +1100, Greg Schwarz wrote:
> One big problem you will have, many ISP's will not let you relay mail via
> different smtp server. This is to stop spam mailers. Most ISP's you dial
> into will only allow you to use their smtp server.
Usually it is the other way around. The ISP you dial into does
not care which SMTP server you use, but the SMTP server you connect
to will only accept your email if it either recognizes you as a valid
sender from the same domain as the server, or if the server is
responsible for accepting email to the recipient of your email.
What this means is that you can usually either use the SMTP server of
your ISP or the SMTP server the email eventually has to be sent to (as
determined by DNS-MX), but not any other, arbitrary SMTP server.
For ISPs to physically block outgoing SMTP traffic to non-local SMTP
servers is relatively rare, because it breaks a lot of default Unix
setups that run sendmail without a "smarterhost" entry. A lot of
ISPs actually prefer you to run sendmail without "smarterhost", i.e.
to connect directly to the destination SMTP server instead of going
through the ISP's server, because this reduces the load on the ISP's
server, in particular if you run and expand mailing lists.