BT have recently upgraded their mail servers to reduce or eliminate the possiblity of them being used for spoofing email addresses. (Spoofing is the term used when someone tries to make to appear that an email has been sent from someone else and is often used by spammers.)
The effect of this is that you will not be able to send email until you have made some changes to your account with BT. To do this, either click the image to the right or log in at the following URL using the username and password suplied to you by BT.
If clicking or double-clicking this link does not work, copy and paste it into your browser as one long address.
The essential box to complete is the one at the top right where you enter your name, company name or both. Actually, enter whatever you want to appear in the From line when your email is received.
You should ignore the request for passwords unless you want to use BT Webmail for handling emails.
Save the information and you should be able to send and receive your email again.