Someone on Discord gave me this advice (I forgot who it was or I would give them credit). 
  
Verification emails weren't coming through to my Yahoo account until about 18 hours after I requested them.  The person on Discord mentioned that he was in a similar scenario but did "one last request" yesterday morning (US time) and it came through instantly.  Being out of options, I decided to give it a shot and figured what the hell.  When I woke up this morning, I saw that a bulk of verification emails had arrived (all requested at some point yesterday and all invalid).  I submitted another verification request (9:30am EST), and magically, it arrived instantly!  I don't know what it is with the Yahoo servers, but perhaps there is some kind of window that allows emails through during certain times?  Whatever the reason is, I would give it a shot.