Re: Multiple domain name support


"-" <kd6lvw@xxxxxxxxx> wrote in message
news:1188373853.124785.98700@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Kees Theunissen wrote:
hec wrote:
I suspect that what I need to do is setup three "virtual" domains
on three separate IP addresses on the current mail server. I am

It's not trivial -if at all possible- to force sendmail to use
the "right" interface/ip-number for outbound messages.

It is possible with some limited success. For incoming messages, it's
possible to bind them to the inbound IP address (and yes, each domain
will need its own IP address for this). Messages that are then
forwarded to other places will be sent with that same IP address as
the outbound source. This is done with the "b" modifier in the
DAEMON_OPTIONS() statement in the "m4" file one uses to generate
sendmail.cf.

I will check that out.

However, I have noted one problem with this - which I have posted
previously, but I don't think our sendmail staff picked up on it: If
the server operates both IPv4 and IPv6, binding to the address also
binds to the address family. This can be a problem for a message
being forwarded to an IPv4 only host that came in via IPv6. Such a
message gets stuck in the queue as it has nowhere to go via IPv6.
It's not bounced immediately ("no route" error) - it just stays
there. (I never left one in there long enough to time out - so maybe
it does eventually get returned tot he sender.)

I think that there needs to be a new modifier that binds a message to
the hostname it arrived on, regardless of IP address. If the host is
set up properly to use the same hostname on IPv4 and IPv6 forward and
reverse DNS lookups, then the above problem can be avoided.

I am not going to worry about this now. I have my hands full with IPv4 they
will
probably have to drag me kicking and screaming to IPv6. So I do not think it
will
be an issue for now.

You are talking now about three domains; a manageable number.
This will certainly not scale to an arbitrary large number of
domains. Although you probably never want to use huge numbers of
domains the ability to scale is an indication of the quality
of a solution. If you can't scale it up it's probably just a
workaround instead of a solution for the problem.

And if each of these domains has SSL'ed web servers, you will already
be using separate IPs (one each) for them anyway....


You are correct. We do have multiple IP addresses and I can easily set the
DNS
MX entries to point to different IP addresses. Currently all three MX
entries point
to the same CNAME and therefore IP address. As for the number of domains, I
do
not see us expanding beyond the three we currently have at least for the
foreseeable
future.

Thanks to both of you for your comments.

Regards, Hugh

--
Hugh E Cruickshank, Forward Software, www.forward-software.com


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