28 Feb
2000
28 Feb
'00
10:53 a.m.
Pete writes:
My ISP runs two SMTP mail servers, one open, the other
not; for a very good
reason. A large number of customers travel across Europe, and it is not
practical for them to always dial the ISP at international rates. Hence,
This can be solved by having your POP or IMAP daemon open up temporary
access to your SMTP server from the roaming IP address after the POP or
IMAP connection is authenticated. This is what I do for some of my users.
If you use qmail there's a readymade program available, but it should be
easy to set it up for Sendmail.
Another approach is for the "roaming" relay to only accept email with both
envelope sender and from headers of legitimate customers. This isn't as
secure, but is still much better than a wide-open relay. If a spammer
discovers the relay by scanning IP addresses for SMTP ports, they still
won't be able to use it unless they also can determine who the legitimate
users of that SMTP server are.
IMNSHO, the disadvantages of the open relay *far* outweigh the benefit.
However, until there's a sensible system to deal
with roaming users' need to
send mail as well as receive it, there will be open relays.
Lots of sites are starting to refuse mail from open relays. Your ISP is
going to have to come up with a better solution.