I have a client that has their own inhouse domain and email server, via a static IP via their ISP "Telstra / now Vodafone"
They send bulk emails (subscribers) and a lot of them are home users with @xtra.co.nz email addresses.
Yahoo has put their IP or domain name on a black list, or maybe telecom business hub has, or both. But it's not possible to speak with yahoo, or communicate in any form outside of the silly bulk sender form, that they don't process. (have done this multiple times) This problem has consistently been an issue for 6 months.
Telecom, wont do much because my client isn't their customer.
All Telstra have suggested is changing their static IP and perhaps temporarily fixing the problem.
meanwhile the xtra customers, can send my client email, but even replies don't get back to them.
I suggested they change to xtra (much as it feels like extortion) but they wont. I'm not surprised, who would ?
How else to fix the issue?