Following installation of BT Broadband you will be able to receive email using Outlook Express but will be unable to send from a non-BT email account. In order to be able to send email you will need to make a small change to Outlook Express. This change is called Authorisation. The procedure is described below. It assumes that you already have Outlook Express set up to receive email.
Step 1: Open Outlook Express, click on Tools and select Accounts...

Step 2: The following new window will open. Highlight your email
account and click on properties.
Step 3: Click on the Servers tab and tick the box entitled 'My
server requires authentication'
Step 4: Click on settings. Following window will open.
Click circle entitled 'Log on using'. Type in your BT username and
password. Click OK.