Last month Yahoo updated their DMARC (Domain-based Message Authentication, Reporting and Conformance) policy basically telling servers to reject all Yahoo email that fails DMARC. In theory this reduces spam, by making sure Yahoo addressed emails actually come from Yahoo. But it also means that you can no longer use a Yahoo address to post to most mailing lists, and you can't use your own or your ISP's SMTP server for Yahoo mail (for instance, sending Yahoo mail from Outlook or Thunderbird).
Yahoo has a solution - but how many home users will be able to do this without technical help is questionable.
(Thanks to Grant Hutchinson on the NewtonTalk list for bringing this to my attention!)
[Ed's Comment: How many of our community have been affected by this and have you found any other solutions to get around the problem?]
(Score: 2, Informative) by Ja'Achan on Friday May 09 2014, @06:07AM
One of our applications sends out email on behalf of other users, we noticed it breaking for one of the users, who had a Yahoo email address. We had to remove the 'send by' in favour of a noreply@ address. Heard about this news quite some time ago, so I knew what to look for.