Re: Networking -- use of two Internet connections for one server with round robin DNS -- web okay, but should I do mail this way too?
Erwan David <erwan@rail.eu.org> writes:
> On 09/07/11 18:15, lee wrote:
>> Andrew McGlashan <andrew.mcglashan@affinityvision.com.au> writes:
>>
>>> Can rDNS lookups for different IPs return the same result such as
>>> "mail.example.com" or must each IP have it's own unique PTR record
>>> name?
>>
>> Apparently they can, though I don't like the idea. For outgoing email,
>> you need to make sure that the hostname given in [E]HLO statements and
>> the IP address of the host connecting to a remote MTA always match when
>> the remote MTA resolves either. You may send me some test mails to
>> check.
>>
>>
>
> My mail server is behind a NAT gateway in IPv4, and directly connects in
> IPv6. What shoud I configure it for HELO : the name of the NAT gateway
> (for IPv4) or its own name (IPv6 only from outside) ?
Hm. Can you send me an email through IPV6? My guess is that you can
not, and that you would need to configure the [E]HLO depending on which
version of the protocol you use to send outgoing messages. But then,
I'd have to look up how exactly exim4 is doing the rDNS checking to be
sure.
> This kind of check is useless and makes loose too many legit emails.
The rDNS check is very useful because it keeps out tons of SPAM without
occupying too many resources. It also seems to be common practise. Do
you have a better suggestion?
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