gmail wrongly rejects mailing list posts as spam

[totaam]

I allowed 3 messages within an hour and all gmail addresses started bouncing the third one with:

<USER@gmail.com>](mailto:USER@gmail.com): host gmail-smtp-in.l.google.com[108.177.15.26] said:
    550-5.7.1 [78.129.163.13      12] Our system has detected that this message
    is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to
    Gmail, 550-5.7.1 this message has been blocked. Please visit 550-5.7.1
    https://support.google.com/mail/?p=UnsolicitedMessageError 550 5.7.1  for
    more information. p8-20020a5d59a8000000b0021849827fccsi5831542wrr.45 -
    gsmtp (in reply to end of DATA command)

We have hundreds of gmail addresses on the mailing list... so hundreds of bounces.

This is where it gets "fun", the chat support was not very encouraging, asking questions that had obvious answers in the log samples already provided or telling me that "I understand that you are concerned about spam emails" when I am not concerned about that at all, only about gmail mishandling emails:

Then a fairly long (10 messages) email thread started regarding this issue, where I had to repeat the same thing again, and again.
Here's a sample exchange:

This is about the issue for not being able to send emails through your hosted mailing list.
As per our higher tier of support, you need to get in touch with your email provider so they can check their server about the said error.
May I ask if you already tried to reach out to them about this case?

No, I do not need to "get in touch with my email provider".
I am my own email provider and I also run the mailing list on that same system.
I do not need to check the server "about the said error" as I've already given you all the details about the error, which comes from gmail's server wrongly rejecting the mailing list messages as spam.

Please fix gmail's spam filter for this mailing list so that I can resume traffic and re-send the message that has been wrongly blocked.

They also tried to "inform" me about the error code, which I had given to them.
On two more occasions, they asked again that I talked to my "email provider". Either this was a different person who had not read the earlier discussion, or just forgotten about it?

Eventually this response came:

The main issue was on Gmail server and our Higher Tier Team doesn't have tools to troubleshoot on this kind of delivery issue since we don't have access to Gmail servers.

Thanks for wasting my time and resources google!

TLDR: don't use gmail to reliably receive mailing list messages.

Edit: It's not like they don't know about the problem either:
Check if your Gmail message is authenticated
: Important: Messages that aren't authenticated aren't necessarily spam. Sometimes authentication doesn't work for real organizations who send mail to big groups, like messages sent to mailing lists.

[totaam]

And again today for this message:
ANNOUNCE xpra-html5 releases: v5.3 and v8.1

[<********>](mailto:********): host aspmx.l.google.com[66.102.1.27] said:
    550-5.7.1 [78.129.163.13      12] Our system has detected that this message
    is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to
    Gmail, 550-5.7.1 this message has been blocked. Please visit 550-5.7.1
    https://support.google.com/mail/?p=UnsolicitedMessageError 550 5.7.1  for
    more information. w6-20020a5d6086000000b0031134a78ed6si1388140wrt.155 -
    gsmtp (in reply to end of DATA command)

[totaam]

Let's hope that google's postmaster tools can help us tell gmail that they got it wrong:

[totaam]

[totaam]

So, they've changed their policy to require DMARC + DKIM. That was all.

The latest mailing list post made it:
https://xpra.org/list/2023-July/002986.html

[totaam]

I sent two messages in the same afternoon:

• [winswitch] [ANNOUNCE] xpra-html5 v10
• [winswitch] [ANNOUNCE] xpra-html5 v5.4

and it's triggering gmail again. Because of course it does, DMARC and DKIM notwithstanding.

[<REDACTED@REDACTED.com>](mailto:REDACTED@REDACTED.com): host aspmx.l.google.com[64.233.166.26] said:
    550-5.7.1 [78.129.163.13      19] Gmail has detected that this message is
    likely 550-5.7.1 suspicious due to the very low reputation of the sending
    domain. To 550-5.7.1 best protect our users from spam, the message has been
    blocked. 550-5.7.1 Please visit 550 5.7.1
    https://support.google.com/mail/answer/188131 for more information.
    q4-20020adfea04000000b003316947d2acsi6291692wrm.250 - gsmtp (in reply to
    end of DATA command)

I was going to try to continue using the mailing list for a little while longer but this may the final nail in the coffin.
I just don't have time to deal with this nonsense, again and again.

Postmaster tools shows no problems (No data to display at present. Please come back later.) and their support page concludes that: If none of the above problems apply, and you've verified that you're sending emails in accordance with our guidelines, you can contact the Gmail team.

[totaam]

Amusingly, the latest release announcement "winswitch ANNOUNCE xpra-html5 v11" did make it to gmail this time, but landed in the spam box, together with an email sent from the GSOC mailing list.
Google's own mailing list was also classified as spam!

[totaam]

And a new one today: Your email has been rate limited because SPF authentication didn't 421-4.7.27 pass for this message. Gmail requires all bulk email senders to 421-4.7.27 authenticate with SPF.
Which is blatantly untrue, SPF has been there for years and years.
The message did get through, just slower than usual.

[totaam]

Google banned our GSoC Mailing List