[Cialug] RFC & best practices for mail server hostnames?

[Paul Gray]

On 2/1/2013 12:55 PM, Dave Weis wrote:
> [djweis at charmed ~]$ nslookup -type=txt statefarm.com
> Server:         67.224.64.31
> Address:        67.224.64.31#53
>
> Non-authoritative answer:
> statefarm.com   text = "v=spf1 ip4:12.34.246.0/24 ip4:204.94.39.0/24 ip4:204.118.102.0/24 ip4:205.166.218.0/24 ip4:205.242.228.0/23 ~all"

I don't know how/why this thread went so awry, but Dave's post here is 
the crux of your answer.

The IP address in the EHLO was 205.242.229.166, which falls within the 
SPF, so it's listed from SF as a valid egress mailer.

There's not an RFC requirement for the IP to resolve, let alone resolve 
correctly back to the original given in the ehlo.  Rather that's an 
administrator's option in Postfix (which you seem to be using) to cut 
down on spam - just as the option to not allow any mail from IP 
addresses belonging to DHCP'd DSL lines - just as the option to not 
allow any mail from IPs found in RBLs.   Standard practice is to have 
PTR records for all IP addresses. However, there is no rule or RFC that 
says that this is required.

In other words, you're not going to find a club in any of the RFCs with 
which to beat up SF.  Rather, your (local) administration policy, while 
I agree with it, is blocking RFC-compliant mail.

To relax this in postfix,

/etc/postfix/main.cf
#smtpd_client_restrictions = reject_unknown_client

-PG