Backup MX - DNS "Fallback"

[MaddinXx]

Hello everyone

Today I tried setting up a MX backup server running ISPConfig.

I just created a regular "ISPConfig mailserver" and configured the mail transport according to posts found in the forums here, as well as relay access.

However I don't get the point on how to configure the DNS.

I have MX 1 with Prio. 10 and MX 2 with Prio. 20 as well as a CNAME mail.domain.tld pointing to MX 1.

Sending mails through MX 1 FQDN or CNAME works well.
Sending through domain.tld (without mail CNAME) doesn't work (no SMTP server found).

So MX 2 doesn't work at all.

Is their something I have to do with the DNS? Normally, it should work sending mails "to" domain.tld as it's suposed to lookup the MX records, or do I miss understand this?

Thanks for your help!
MaddinXx

[falko]

You must not use CNAMEs for MX records. MX records must always point to A records.

[MaddinXx]

Hi falko

Well, at the very end they do point to A records. What I have is:

mail.domain.tld -> CNAME to -> mail.alpha.otherdomain.tld
mail.alpha.otherdomain.tld -> MX -> Prio. 10
mail.beta.otherdomain.tld -> MX -> Prio. 20

mail.alpha.otherdomain.tld -> A -> to mailserver IP
mail.beta.otherdomain.tld -> A -> to 2nd mailserver IP

Both mailservers are running on other servers than the webserver.

[falko]

Why do you use an MX record for mail.domain.tld? it should be domain.tld unless you use email addresses like user@mail.domain.tld.

[MaddinXx]

Hi falko

The CNAME is for the tld itself. I've attached the two DNS zones:



and

[falko]

The DNS records look ok.

Sending mails through MX 1 FQDN or CNAME works well.
Sending through domain.tld (without mail CNAME) doesn't work (no SMTP server found).

For my understanding: sending mails or receiving mails - where is the problem?