Help with MX records

praveen

Client is running exchange server in his office and need to have a backup mail 'catchall' account on the cpanel server. That is when the exchange server goes down all emails will be delivered to the catchall account.

Now my bind DNS entries are like this

20 mail.domain.com xxx.xxx.xxx.xxx

100 backupmail.domain.com xxx.xxx.xxx.xxx

Now client need to have an option that is, when the primary mail server ( Exchange server) is down for more than 24 hrs then only mails should deliver to the backup,

is this possible? Is something to do with Retry?

can you help

aglodek

Seems to me your DNS entries take care of that. If primary is down, all email will be delivered to backup. Only thing is, they will get delivered there not after 24 hours, but right away, once primary is offline. The catchall account needs to be configured on the backup mail server. Please note that once the primary is back up, the backup will forward all email there.

Edit: at least that's how it's supposed to work - haven't tried this out myself yet

Maounique

http://www.junkemailfilter.com/spam/free_mx_backup_service.html

praveen

Thanks friends, let me have a look

xDutchy

@andrzej actually that statement is in most cases false.

A mail server usually tries to deliver an e-mail for a set period of time, usually 24/48/72h depending on its configuration.

After that it will deliver the e-mail to the 2nd mail server and depending on its configuration do something with the e-mail.

aglodek

@xDutchy: interesting. I stand corrected

However, this doesn't make much sense to me. If first (in order of priority in DNS) MX is down, email should be delivered to the next MX in order of priority, which, as you correctly pointed out, will do something with it, depending on its configuration. My statement in my previous post assumed the backup would be configured accordingly, that is to deliver to primary once primary is back up. Apologies for my "shorthand" there

Anyways, I'm planning on testing how this works in actual practice with a primary and backup MX (using a Virtualmin/Postfix/Dovecot setup) - so will know for sure

praveen

i made some search but didn't find any proper answer for my query.. i learn that most of the email servers try to deliver mail and keep in queue at least for 12 hours before bouncing back and my client says he is not expecting any downtime more than 6 hours for any reason.

So i just removed the backup MX record and have only the primary one to avoid the issue of mail being delivered to the 2nd server.

@Maounique thank you for the link, i will use this for another client..

emilv

If the first MX doesnt respond it will try the next one right away.

aglodek

@emilv said:
If the first MX doesnt respond it will try the next one right away.

This was my understanding, too, and this makes perfect sense