We have a remote sending domain complaining to us email was rejected by bad reputation (ironport).
Normally, this is contributed by remote incorrect dns setting (missing reverse mapping).
This is one very common issue and it's off my back.
We checked further that it looks like their dns hosting has AAAA record on its nameserver ip.
The sending mailhost does _not_ have AAAA record.
We are being suspicious only. because our own dns server is still running bind/named4.
In "sendmail", there was/is a setting to manage "brokenAAAA" record, but we have nothing to relate this case.
As IPV6 is becoming a new issue. I have this question for Ironport
- Do ironport itself needs to be IPV6 ready? (your replies seem there _is_ a need for upgrade)
- Mail traffic mostly depends on DNS lookup, what are the requirement for DNS server / resolver if this is need to be
used by Ironport.
Example: Some DNS server may return AAAA record first before A record.....
- Another confusing issue seems to be, we can still have AAAA record even IPV4 only network?
