Yahoo no longer showing mobile view since last week?!

Damn, first time I've logged into Yahoo in at least six months (this is a test account only) and the first time on a phone, the mobile site is slick.

Back to the issue....
Have your emails ever been tested for this scenario?
I only ask as it was always the recommendation from the industry to never expect any good results from viewing an email in the webmail version of your email client, on a smartphone.

Webmail is specifically built for desktop use.
This isn't to say webmail clients cannot work on mobile, but because they are purpose built desktop experiences, responsive support was never a native feature. Gmail was always notoriously bad at this.

I could be completely wrong at this point in time, in late 2019.
My points above are going on pre-2018 knowledge and experience. 2018 because it's been at least two years since I've seen this type of issue raised.

Email clients may have upped their webmail in mobile browser game since 2018 and you may have tested this and it worked and Yahoo may have made a recent change to revert back to not supporting this scenario anymore.

If you haven't tested this scenario and are expecting it to work the same as any normal mobile website, I'm sorry to disappoint.

I wouldn't expect much from webmail clients on mobile at all.
To be honest, I don't blame these providers for a lack of support. These devices are built to support native app experiences and they invest a lot more into a well optimised mobile app that can work with the features of the phone.

However, I totally understand when people don't want to bog down their phones with loads of apps and prefer to access certain services via the mobile browser so it's easy to simply close the tab and move on with your day is a lot less hassle.