Check if your sender domain or IP is listed on Spamhaus. Ask them to send a blank email to see whether you can receive it or not - perhaps they include an attachment, characters or other elements that may cause the rejection of their email.
I have the same problem and with multiple providers
Error: “553 5.7.2 [TSS09] All messages from 126.96.36.199 will be permanently deferred; Retrying will NOT succeed. See https://senders.yahooinc.com/smtp-error-codes/” while connected from jesepe.uneafuseauean.xyz (188.8.131.52) to mta5.am0.yahoodns.net (184.108.40.206)
I tried every method / solution and best practices and nothing works !!
so if anyone have the same problem or have the solution ill be appreciate