Are any of the other affected users on a paid Yahoo Mail subscription? If so, reaching out to Yahoo Customer Care directly may help - you can message them on Facebook. I've already sent a message but I'm guessing that the more complaints they receive, the more likely they will be to actually resolve this issue.
Links:
Australia -
https://www.facebook.com/YahooCustomerCareAustralia
Indonesia -
https://www.facebook.com/YahooIndonesiaCustomerCare
Other countries -
https://www.facebook.com/YahooCustomerCare
(These are the only search results for "yahoo customer care" on Facebook.)
This is the message I sent... if you're contacting them please vary it up a bit, don't just copy'n'paste mine directly:
"Hi Yahoo's mail servers have been blocking incoming messages from ZoneEdit for several days now. ZoneEdit has requested unblocking but the problem persists. This is causing problems for many ZoneEdit users who use Yahoo Mail, and many users with paid subscriptions to Yahoo Mail (including me) are considering cancelling our paid accounts if this continues. Can Yahoo please unblock ZoneEdit's servers?"