Simple question on DNS

noir911 · 10-16-2008, 06:40 PM

If I have four MX record for domain.com in the order of 10 (mx1), 20(mx2), 200 (mx3), 200 (mx4) then if mx1 and mx2 are offline, will mx3 and mx4 still deliver the email or they will just queue the email and wait for mx1 and mx2 to come back online?

All the mx's are configured to send and receive emails.

Thanks.

uncle_philip · 10-16-2008, 09:46 PM

under my understanding, mx2, mx3, mx4 will only queue the mail.

JimBass · 10-16-2008, 10:44 PM

That goes against my understanding. What low priority mail servers do with the mail is controlled on those servers, not by the DNS.

You can configure any mail server to queue the mail, but that needs to be setup.

Peace,
JimBass

Mr. C. · 10-17-2008, 12:14 AM

Quote:

Originally Posted by noir911

All the mx's are configured to send and receive emails.

MXs receive mail. If the same server also happens to send, that is inconsequential to the concept and role of an MX.

uncle_philip · 10-17-2008, 12:22 AM

This is what I observe from my mail-server,
when mx1 is offline, mx2 will queue all the mail.
when mx1 is too busy, mx2 will queue parts of the mail, then mx2 will communicate mx1 on every periods of time to see if mx1 is healthy, when mx1 is back to normal, mx2 will send all the mails to mx1.

Mr. C. · 10-17-2008, 01:03 AM

An MX accepts mail - what it ultimately does with that mail depends on how it is configured. It can relay the mail to a higher priority MX, or it can deliver the message to a mail store.

chort · 10-17-2008, 02:08 AM

Quote:

Originally Posted by uncle_philip

This is what I observe from my mail-server,
when mx1 is offline, mx2 will queue all the mail.
when mx1 is too busy, mx2 will queue parts of the mail, then mx2 will communicate mx1 on every periods of time to see if mx1 is healthy, when mx1 is back to normal, mx2 will send all the mails to mx1.

That means that the MTA on mx2 was intentionally configured to send mail to mx1 instead of attempting to deliver it to a mailbox. That has nothing to do with DNS.