Hyperlinks are not working in any email app.

I would start threads for each. Store likely needs to be reset.

Not following what you mean you cannot create Yahoo Mail account in desktop app.

Which desktop app? There is a yahoo mail app, does it work?

The issue first appeared in the Windows Mail desktop app with 2 email accounts needing to be fixed (password refreshed), one recovered OK but not BTYAHOO Mail. Eventually I was advised to uninstall and re-create it. But I have not been able to add / create BTYAHOO. At first I assumed it was a fault with Mail itself so I contacted MS Support, but then discovered I was unable to create / add BTYAHOO in any other desktop email app either, including YAHOO MAIL app itself. This 'proves' the fault is specifically with YAHOO, yes? YAHOO Help could not help and passed the buck to BT (BT is my ISP). So far after some hours on both chat and phone BT have not been able to resolve the issue, and eventually said they only provide support for issues with their online service (which fortunately is OK) not with any desktop apps.

This leaves me in limbo and dissatisfied with both BT and YAHOO, so I have submitted a formal complaint to BT using their customer complaints form. I am now waiting for a phone call from BT scheduled for next week. I realise their advisors have encountered an unfamiliar problem with this, but if it cannot be resolved I will have to abandon BTYAHOO which I have used for over 20 plus years and find another provider. I have also given them another prod by drawing attention to the situation on Twitter!

STOP PRESS! When composing this reply a few minutes ago another solution occurred to me. In the Mail app menu for adding new accounts, where Yahoo is listed, there is another option at the bottom of the list. It is 'Other'. I tried this and it worked!

Excellent.

I wonder what you are doing "Manually" within Other setup that is being done differently when you use the automation to setup a Yahoo account?