Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Same problem on my iPhone and iPad. It’s so bad that now I sign-in to the web version several times a day to make sure I don’t miss any emails.
 
Yahoo mail still not working with new update yesterday. I thinks it’s an Apple iOS 11 issue because always worked before
 
I'm glad I found this thread. This has been driving me nuts for 3-4 weeks now. None of the email will come in, and then suddenly it all appears. I've wiped my phone, installed 11.3, uninstalled 11.3, wiped my phone, reset my yahoo mail password, basically gone through every step I can to see if there was a resolution. I don't want to use their crappy app and much like others, I've used/had this address for 2 decades, so changing it would be time consuming. I just don't get what changed and broke this.
 
The weird thing, Yahoo mail won't update on my iPhone X but will update fine on my iPad.

Same here. I have both devices set to fetch every 15 minutes. It doesn’t work properly on my iPhone X. I basically have to manually pull my emails. It fetches fine on my iPad.
 
Yahoo Mail on my 8 Plus has been fetching just fine now for the past couple months...knock on wood.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.