Sendmail on a LAN
jd1008 at gmail.com
Tue Aug 17 21:25:07 UTC 2010
On 08/17/2010 01:27 PM, Gordon Messmer wrote:
> On 08/17/2010 09:33 AM, JD wrote:
>> Re: a.b.c.d ==> valid.host.name
>> and valid.host.name ==> a.b.c.d
>> does not seem to apply to the google smtp server I use for Thunderbird.
> You did your test entirely backward. You did a forward lookup first,
> and then checked the PTR of the IP which was returned. There is no
> requirement for a PTR to match every hostname that resolves to its IP
> Let's finish your test:
> $ host smtp.gmail.com
> smtp.gmail.com is an alias for gmail-smtp-msa.l.google.com.
> gmail-smtp-msa.l.google.com has address 184.108.40.206
> The result of this test merely identifies an IP address. Now, let's
> test to validate that the IP returns a PTR that resolves to the same IP:
> $ host 220.127.116.11
> 18.104.22.168.in-addr.arpa domain name pointer px-in-f109.1e100.net.
> $ host px-in-f109.1e100.net.
> px-in-f109.1e100.net has address 22.214.171.124
> Yep, totally valid. That IP address has a PTR record, and the hostname
> contained in that PTR resolves back to the same IP address. This host
> is properly configured.
>> So, Thunderbird client does not seem to mind that
>> reverse lookup does not match the name smtp.gmail.com
> Clients rarely do. It's the servers to which you're going to try to
> deliver mail that will mind.
I see! Thanks for the heads up!
At any rate, I am having serious problem with an unwieldy router.
I just posted a message about that.
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