I've seen problems like this because of ISP listing large net locks as "dialup"
and not supposed to send email directly.
Check spamhaus' PBL:
https://www.spamhaus.org/pbl/
Best regards
El 30 de diciembre de 2023 7:40:59 CET, Simon Wilson via mailop
escribió:
>I know, I'm not alone in this... :(
>
>I like to think that it's still feasible to run one's own email. I have for
>many years, and currently manage about a dozen email domains for family and
>friends. Most of the time all good.
>
>Then today my dad says to me "Why am I getting these bounce messages?"
>
>I check, and Gmail are deferring an email he sends every week to a group of
>friends, 20 all up, 15 of them on Gmail, saying his SPF domain is a source of
>unsolicited email (421-4.7.28). Outlook and Hotmail accept OK.
>
>This domain is old, not compromised, has SPF, DKIM (1024bit), DMARC, all
>valid. We send using TLS. We have correct PTR. His emails go out fully signed
>and pass checks. We don't send commercial emails, and that domain name is low
>volume and all emails individually written and sent through a webmail client,
>none of it is automated.
>
>Are we wasting time even trying any more?
>
>You can't even submit a request to them for help, because they ignore it
>unless you attach valid and current mis-classified headers from within gmail.
>Umm.. how can I do that when they're not accepting the email?
>
>Simon Wilson
>M: 0400 121 116___
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