Creating a secondary exim server in case first goes down

D

djcronos

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Mar 21, 2006
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Hello,

I was wondering if anyone knew of a tutorial or howto on creating a secondary mail server on another machine (without directadmin) in case our DA machine goes down and needs to route mail.

Thanks in advance.
 
Your DA machine will have problems routing email if it's down :) .

You can google some secondary MX configurations for exim, but unless you have a list of valid users on your slave server you'll have to accept email for everyone, even non-existent users.

Then when your main server comes back up and won't accept the mail for non-existent users what will you do with it? You can't send it back.

Jeff
 
Yes it is possible to do it, it's called 'clustering'. Never had to do it though. I know webmin can manage an email server cluster.

You'll have to replicate all your mailboxes to both servers all the time (I think) so in case on goes down, the other will have the same content. Then you can setup a second MX entry with a lower priority in your DNS record.

Let me know if you find a howto about this.

Regards,
Stéphane Brault
http://www.homemusician.net
 
will this possibility work and or problems ?

have and external email (main) server, with all the frills, etc (windoes - mdaemon and all its addons)... so iam thinking of using one of my da servers for email backup.... so dns mx points to the external or main server, so i will put a second mx record in dns (this is external also) with a higher mx priority (20) the main is (10) and then create domains under an account on the da server to match the ones on the main server,,, i know i will have to dup all email accounts and domains that i want to backup, this is i hope will allow domains/user that are setup on the da srv. to continue receive/send email in the event that the main server is down for a period of time... no dns will point to these da domains except the dns mx record, not trasfer of rec email just a backup if the main one fails... thoughts etc. help more needed... note: the da server itself does resolve,,, so i think this might server as a (simple) short term backup in this scenario... your thoughts....

chuck:eek:
 
hendrix74 said:
Yes it is possible to do it, it's called 'clustering'.
Click to expand...
Having secondary MX server(s) for email has nothing to do with clustering.
Never had to do it though. I know webmin can manage an email server cluster.
Click to expand...
And will most likely totally destroy the DA configuration in the process.
You'll have to replicate all your mailboxes to both servers all the time (I think) so in case on goes down, the other will have the same content.
Click to expand...
No, you don't have to do that; you set up a secondary MX configuration and the slave will hold email until the primary is available. You don't want the slave to keep mail because if it did each of your users would have to check mailboxes on both servers each time they check email, or else they'd never get all their email.
Then you can setup a second MX entry with a lower priority in your DNS record.
Click to expand...
Not if you've got a cluster; if you have a cluster then the clustering software handles the delivery.

But yes, if you've got a seconary MX server. Which has it's own set of problems. Fpr example, your idea of duplicate mailboxes except for how users would get mail from both servers.
Let me know if you find a howto about this.
Click to expand...
There are plenty of HowTos on the net for using exim (and just about any other MTA software as well) as a secondary MX server.

Most of us have given up on the idea though because of the issues involved in keeping track of users to accept mail for, and users to bounce.

Because if we accept email for non-users, then we're stuck with it when the primary mx comes back up. It won't accept the mail, we can't return it because we don't know if it's really from the purported sender or not, and RFCs don't let us destroy it.

The right way would be to continually update all users on the primary mx to a list the secondary mx uses to know how to accept mail for. Easier said than done.

Jeff
 
hostu, if you create an mx record for a domain that mx server WILL get at least some email for that domain. How will your users get the mail from that secondary server?

Jeff
 
h2d said:
www.rollernet.us
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I can't find any information on how they verify if an account is valid before accepting email for it.

Do you know how they do that?

Also, there doesn't appear to be any way to find out pricing without signing up first. Do you have their pricing?

Jeff
 
jlasman said:
hostu, if you create an mx record for a domain that mx server WILL get at least some email for that domain. How will your users get the mail from that secondary server?

Jeff
Click to expand...
well, i assume (dangerous i know) that if the first server goes down then the dns will point the mx to the second one - da server with the same domains and email setup, so if my email program (outlook or whatever) points to mail.domainname.com then it would find the new server because the mx records for the higher mx number points to the now new mx ip, i might need to look at this a little more as you got me thinking past what i had done so far,, i did setup an account with www.rollernet.us and may pursue that avenue, but sill looking for any help / advise ... thanks for your reply

chuck
 
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jlasman said:
I can't find any information on how they verify if an account is valid before accepting email for it.

Do you know how they do that?

Also, there doesn't appear to be any way to find out pricing without signing up first. Do you have their pricing?

Jeff
Click to expand...


Hi

There are many different methods u can choose to receive mail for on there secondary mx
( they also do secondary dns )

I suggest signing up, its free to check them out :)

If your satisfied with the services they offer, it only costs 34.95 US per annum
 
hostu said:
well, i assume (dangerous i know) that if the first server goes down then the dns will point the mx to the second one - da server with the same domains and email setup,
Click to expand...
Is there some superintelligence out there on the 'net somewhere called DNS?

Unless you know something I don't know, DNS is merely a database lookup service running on one or (hopefully) more systems.

And during changes DNS will not be the same all over the 'net; changes take time to propagate.

So it's likely there's going to be email on both servers almost all of the time.

Jeff
 
h2d,

I created an account, and I can't figure it out yet; you don't get any real instructions on how to use their maps, and unless you add a domain you don't even see how it works.

:(

Jeff
 
sorry to have crossed over your wires, i only meant that because the mx records in dns point to the lower mx 10 and only failing i assumed that the email would go to the mx 20 ,i have no question as to if mail would reside on one or both servers etc. thanks for whatever, i guess i came to the wrong place and or post to expect anymore than i have in direct dealings with some on this forum, please excuse my request for help and or gudiance etc. and accept my apologie to any i have possibiliy offended ...

end of my post / comments on this matter....:confused:
 
hostu, it was not my intent to offend you. If I did, please accept my apology. And you certainly didn't offend me.

I just want to point out that if you have mailboxes on a server you'd better have a way for your users to get the mail out of them, because there's nothing magic that'll make that happen.

We have a very important email site. It's posted on two servers with duplicate mx records of the same cost.

And their users check both machines every five minutes.

Jeff
 
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