Suresh Ramasubramanian wrote:
> Varun Varma wrote:
>> The advantage of using CNAMEs is contained in the message above - the
>> MX resolution for mail.abc.net would be the same as for abc.net, so if
> you should never point MXs to CNAMEs - it is just not done, for a
> variety of reasons.
Please read my orginal post carefully - that's not what I am suggesting.
I am saying that setup mail.abc.net as a CNAME for mail.net, which
certainly isn't the same as pointing the MXs to CNAMEs. What will happen is:
The DNS resolver subsystem will send a query to lookup the MXs for
mail.abc.net and the DNS would point out that mail.abc.net is a CNAME
for abc.net. Depending on how the DNS is setup, either the client side
resolver would then resend the query as MX records for abc.net or the
DNS server would fetch this for the client and directly return the MX
records for abc.net. Either way, the MX entries for abc.net would be
I think you are getting mislead by the hostname - "mail.abc.net",
perhaps implying to you that it is the MX also, which isn't the case.
"dig mx mail.mindsw.com" as an example.
Aslo, I really hope you have been following the entire thread.
> As Devdas suggested set up virtusertables.
>> MXs of abc.net change or are dynamic, then you don't need to go about
>> updating your A records. This becomes particulary important when you are
> You are confusing dynamic DNS with cnames, somehow.
No. I am refering to providers like XO, which rotate their MXs [atleast
> And you really must not use dynamic IPs for your MX - at least if you
> value the fact that your email must reach you.
My bad - I should have used the term "rotating IPs" instead of dynamic IPs.
> If you have poorly or intermittently connected hosts (dialup / isdn /
> dsl with dynamic IP), then use uucp - it is an old protocol but still
> quite useful. Run over tcp (and optionally, over ssh tunnels) it is
> quite reliable for what you need to do.
I have never used UUCP and don't really know what advantages it has.
But, I think you are mixing issues here. The OP never said that he has
only part time connectivity - that's just your assumption.
>> Try a "dig MX xo.com" at regular intervals and you'll see what I mean.
> You are completely missing the point here.
Au contraire. You sure you have been following the thread?
>> Er..in the case of the OP, what particular advantage does this
>> approach have over using the aliases file? Expect him having to do
>> more work in setting up virtusertable support...
> What extra work?
The extra of having to understand how virtual domains work under Sendmail.
>> The solution I was looking for is kind of fallback relay that PostFix
>> and Exim support. AFAIK, mailertable in sendmail won't do the job
>> since that defines the routing for an entire domain.
> FallbackMXHost (or confFALLBACK_HOST) is what you are thinking of.
> But that still wont help you .. virtusertable is completely different
> and can provide the per user routing that you want.
Please, please, please tell me that you have read my original post. To
quote from it:
Generic solution for all MTAs: Create aliases/rewrite rules for offsite
addresses. E.g., for sendmail, in /etc/aliases:
As you can see, I have clearly suggested per user routing.
> And if you are using the virtusertable to route mail between poorly
> connected hosts and a central smarthost type system, you are far better
> off setting up the poorly connected hosts as uucp nodes and spooling
> mail for them.
Again, you are assuming poorly connected hosts. That's not been
specified anywhere by the OP.
BTW, is it my imagination or does a "dig mx outblaze.com" only return
one MX, the MX has only one A record associated with it? What I am
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