Sending Failed from Yahoo Bizmail using stock mail app

[Renee33]

Hi, I have both my Gmail and Yahoo Bizmail accounts running into the stock mail app on my S4. This has worked great until a few weeks ago, when it stopped being able to forward or reply to Bizmail messages. When I try, I get a 'Sending Failed' message. Gmail reply and forwarding still works fine. Bizmail messages seem to be coming in just fine; I just can't do anything but read and delete them.

What I have tried so far:
Changing the outgoing mail port. It is set up to use 465. I tried both 587 and 25 but it can't connect during setup with anything but 465.
Changing the outgoing server to the verizon server. Again, phone can't connect during setup.
Deleting the Bizmail account and resetting up. No change.
Rechecked my Yahoo settings, and they are set to allow forwarding
Also tried downloading and running the Yahoo app, but it apparently doesn't support Bizmail (what's up with that?)
If I set Bizmail as the default address from which to send messages, then newly composed messages also fail to send.

So, anybody had this issue? What do I do next?

Thanks for any help!

 

[Renee33]

So, for anyone who might be interested, I ended up calling Verizon tech support. The issue was apparently changing the security setting from SSL to SSL (accept all certificates).