In recent weeks, Yahoo and AOL changed the DMARC policy to proactively protect their users from increasing email spam that uses Yahoo or AOL users’ email addresses from other mail servers. This is an important step to secure their email identities from being used by unauthorized senders.

Right now, the only way to send mail using an from @yahoo.com or @aol.com addresses to domains checking DMARC is to send mail using AOL or Yahoo SMTP servers. The solution is to send your emails 'from' a different email address (i.e., not one with the domain @aol.com or @yahoo.com). This will bypass the whole problem, and ensure that participant HQ emails aren't getting blocked because of this new policies.

Here are some links explaining the issue in detail:
<https://help.yahoo.com/kb/SLN7253.html?impressions=true>
<http://postmaster-blog.aol.com/2014/04/22/aol-mail-updates-dmarc-policy-to-reject/>