*.googleusercontent.com should not only not be sending email (either
change PTR, or use a relay) so you can go beyond scoring, and simply reject.
Also, given the history of abuse and/or compromises, we also recommend
that you do NOT allow email authentication from those IPs, except as
permitted in an allow .acl.
Make sense?
On 2025-09-16 07:58, Scott Q. via mailop wrote:
Sorry for reviving an older thread, we are still battling this Google
spam issue.
Anyone else scoring e-mails directly received from IPs with a PTR of
*.googleusercontent.com ? Any downside to doing this ?
Gmail/Workspace doesn't use that PTR but are there legitimate Google
services that do ?
Thanks!
Scott
On Thursday, 04/09/2025 at 16:21 Alex Burch wrote:
They might have legacy accounts where port 25 is unblocked. I think
Infusionsoft/Keap had their IPs hosted at GCP at one point and they
had the port 25 block lifted to send with them.
Thanks,
Alex
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On Thu, Sep 4, 2025 at 9:12 AM Scott Q. via mailop
<mailop@mailop.org <mailto:mailop@mailop.org>> wrote:
I get that, but the question is more whether GCP blocks outbound
port 25 or not.
Their docs say they are blocking it:
https://cloud.google.com/compute/docs/tutorials/sending-mail
<https://cloud.google.com/compute/docs/tutorials/sending-mail>
yet we see evidence to the contrary. Surely it's a configuration
mistake somewhere (?).
Maybe someone from Google can shed some light on this.
Thanks!
On Thursday, 04/09/2025 at 11:25 Michael Peddemors via mailop wrote:
Careful.. the list admins don't like us using this list to
complain
about spam, but yeah..
Anything with a PTR of 1.132.64.34.bc.googleusercontent.com
<http://1.132.64.34.bc.googleusercontent.com>. is suspect,
and should be rejected (port 25) ...
Standard ruleset for a couple of years.. but even more
important, is the
number of IPs in those ranges used in email hacking, and BEC
Compromise
attacks.
You might even like to block attempts to other ports by
default, and
create a 'permitted' acl for IPs in those ranges for
legitimate use.
On 2025-09-04 07:55, Scott Q. via mailop wrote:
> Anyone else seeing an uptick lately of Spam e-mails
originating from
> these ranges ?
>
> 34.64.132.0/22 <http://34.64.132.0/22>
> 35.240.0.0/13 <http://35.240.0.0/13>
>
> Mostly e-mails with: Content-Type: text/plain;
charset="iso-2022-jp"
>
> What's interesting is that GCP has outbound port 25
blocked by default
> yet these hosts are able to do direct-to-mx deliveries.
>
> If anyone from Google is reading this - can you have a look ?
>
> Thanks!
> Scott
>
>
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