IPv6 connectivity to mx[1-4].smtp.goog.

Tue Feb 27 15:22:37 UTC 2024

We are seeing the same, but seems like it's mostly affecting delivery for broadcom.com, and a few other smaller domains.  However, connectivity to the MX listed by gmail.com (and most other domains using GSuite, etc) are working fine over IPv6.

You may also want to ask the mailop list.

-- 
Alex Brotman
Sr. Engineer, Anti-Abuse & Messaging Policy
Comcast

> -----Original Message-----
> From: NANOG <nanog-bounces+alex_brotman=comcast.com at nanog.org>
> On Behalf Of Marco Davids (Private) via NANOG
> Sent: Tuesday, February 27, 2024 8:03 AM
> To: nanog at nanog.org
> Subject: IPv6 connectivity to mx[1-4].smtp.goog.
> 
> Hi,
> 
> At
> https://urldefense.com/v3/__https://internet.nl__;!!CQl3mcHX2A!Dc9AZo4F
> nrpVmuo3Ehg5iQUAd4uTAsCdz9MWYKJqFWyWK7_XnaDnWN3_DkOAVq2e5
> CXVOb2triASeebvdg$  we're seeing IPv6 connection issues on TCP port
> 25 (SMTP) to mx[1-4].smtp.goog.
> 
> Either 100% DROP (so no TCP connection) or ⅔ failure to setup connection.
> 
> Further testing seems to confirm the problem is bigger and on Google's side.
> 
> So, this fails:
> 
> echo 'quit' | nc -6 -w 3 mx1.smtp.goog. 25
> 
> and this works:
> 
> echo 'quit' | nc -4 -w 3 mx1.smtp.goog. 25
> 
> (on MacOS use -G instead of -w)
> 
> Is anyone else seeing this? Any idea what is causing this?
> 
> --
> Marco