Is There A Short Cut?

[lynbrown]

Every time I open my BT Yahoo email account, I have to sign in with email address and password. is this necessary?

[Old_Geezer]

If you are not using a client, which sends the password for you, then generally speaking, yes. Security.

One thing you can do is leave it logged in on your PC.

[chelle7272]

Can you tick 'stay signed in' on the log in screen?

[Buenchico]

Webmail services are configured to automatically log users out after a period of inactivity (which is often as short as 10 minutes). The way around it, on a PC, is to use a dedicated email client and to have it configured to log into your account automatically every time you open the client. The obvious choice on a Windows PC is Thunderbird:
https://www.thunderbird.net/en-GB/

Alternatively access your mail via a mobile device (such as your phone) where you're always logged into your account. (Security is provided by the phone needing your fingerprint or password before you can use it, rather than by the email service).