exim: multi level MX routing how?

[danellison]

Greetings all. I am a sendmail guru from WAY back and am new to both directAdmin and exim so please forgive any misconceptions I may be dragging forward with me To set the stage so to speak: I am migrating our customer sites from a cpanel environment hosted at AIT.com to our own directAdmin server. I have DNS resources set up like this:

mydomain.com. IN A 1.2.3.4
mail.mydomain.com. IN A 4.3.2.1

- and -

mydomain.com. MX 0 mydomain.com.
mydomain.com. MX 10 mail.mydomain.com.

The idea here is that mail.mydomain.com. will accept mail for our domains in the event that mydomain.com. is unavailable, queueing the messages until mydomain.com. becomes available again and then forwarding the queued mail to mydomain.com. because of it's lowest level MX record. Always worked fine with sendmail but I don't understand how to setup this type of routing in exim

I have searched and read but I must be missing something. Any guidance or pointers to example exim configurations that could shed some light on how to accomplish this would be greatly appreciated.

Thank you in advance for your time and thoughts.

Regards,
Dan Ellison

 

[nobaloney]

Lots of threads on this subject on the forum. I usually butt into each one of them and explain why I think it's a bad idea.

Mostly has to do with dictionary attack spam being sent to nonexistent users. What does the main server finally do with it when it gets it?

Jeff

 

[danellison]

I actually noticed another post on this subject exactly at the same time as I posted my query. I wasn't able to locate anything in a search prior to that however....

The main server (for the time being) actually delivers the message to a local mail box. However, in the next two weeks the roles will be reversing as I migrate over to directAdmin. Once migration is complete the alternate MX record and server will go away. Just trying to make the migration as seemless as possible for our users....

I am aware of the possibility of an attack when running without any user authentication but since the role is basically a backup to the main server it should only kick in if either directly attacked or if the main server is down right?

Thank you for your thoughts and time.

Dan Ellison

 

[nobaloney]

Yes, it only gets used when the main server is down. Which means whenever it's used it's broken.

And of course the above isn't wholly true; most spammers send email to ALL MX servers (mail exchange servers) for the domain; they like backup mail servers because they know they'll accept the email.

Jeff