Frontier has also contracted with Yahoo Mail, and Yahoo is refusing our mail for Frontier:
May 3 15:00:57 mail postfix/smtp: E17491994: to=<REDACTED@frontier.com>, relay=mta7.am0.yahoodns.net[188.8.131.52]:25, delay=150175, delays=150143/0/32/0.01, dsn=4.7.1, status=deferred (host mta7.am0.yahoodns.net[184.108.40.206] said: 421 4.7.1 [TS03] All messages from 220.127.116.11 will be permanently deferred; Retrying will NOT succeed. See http://postmaster.yahoo.com/421-ts03.html (in reply to MAIL FROM command))
That link redirects to: https://help.yahoo.com/kb/postmaster421-ts03.html
Which provides the helpful information:
Sorry, the page you requested was not found.
We suggest you visit Help Central
… Help Central has not been the least bit helpful. I would ask people to see this article:
We haven’t had any more problems with compromised accounts since the Thursday before Last, April 24th, yet Yahoo continues to block our e-mail, and since they are now providing e-mail for ATT/SBC Global and Frontier, this affects those providers as well.
I’d ask you folks, if you have a Yahoo, ATT/SBC Global, or Frontier account, please generate a support ticket and/or complaint there. Please spread the word about Yahoo’s practices. There has to be a better provider ATT/SBC Global and Frontier could contract with and actually get functional e-mail for their customers.