Author: W B Hacker Date: To: exim users Subject: Re: [exim] Gmail and Google blocking inbound port 25?
Mike Lyon wrote: > Howdy,
>
> I know this isn't an exim related question but it's affecting the ability
> for my exim install to deliver email... Anyways, It appears when my exim
> install tries to deliver email to Google or Yahoo, both of them refuse the
> port 25 connection from my host. I went to another server I have in a
> different subnet and was able to telnet to port 25 at both Google and
> Yahoo. So it appears they are blocking this one subnet I have from
> connecting to them.
>
> How does one resolve this issue?
>
> Thank You,
> Mike
'Stock' answer is to investigate the subnet with a 'whois' and see how
it is allocated. If 'AP' - as most 'residential' connectivity pools, and
all-too many so-called 'business' broadband are, then check also RBL's
such as SORBS and the like that target dynamic-IP block ranges.
These are sometimes 'discovered' and other times voluntarily listed by
ISP who have a ToS that prohibits running MTA etc - then operate an MTA
on a different block for use of their connectivity pool subscribers.
Hard to get around that. Potentially harder yet if it is a
Google-specific LBL. Several majors, such as the former 'Baby bell' in
the US, are doing that now on perfectly good IP blocks, sometimes purely
on a basis of GeoIp or host country of the block holder.
I'm presuming, of course, that with your experience level, you already
have a valid non-generic, FQDN-relevant, PTR RR and matching MX DNS
entries. Absent that, a BL needn't be checked, as a vanilla reverse
lookup fails.
