Add email to MyBT?

[Frogmodem]

I am being offered the option of adding an email account to MyBT.  I can see all my accounts in the list already when I log onto MyBT so what does 'adding' an account actually do?  I can see that my main account and one sub-account have this option but one doesn't, so does that mean that it's already 'added'?  

[gg30340]

Where is this option to add an email account to your MyBT appearing? 

You can add other email accounts, either BT ones or ones from another provider to your BTMail account so that when you access your BTMail account the email accounts that you have added to it appear below the folders list on the left hand side.

This allows you to access those accounts via your BTMail account by clicking on the "added" accounts name,  which in effect has your BTMail account working in the same way as an email client/app where you can set it up to access all your email accounts in one place.