So the password change didn't work (No surprise really). I spoke to BT again and got a totally different response - one which I am more inclined to believe. My wife sends a few emails every day - about a dozen or so. This apparently is seen by BT email as worthy of flagging as hacking attempts. As a result of this, a soft lock is put in place on the account which clears after a period of time (not sure of the duration though). The soft lock prevents the sending of emails.
The conversation with the BT agent then went on to the fact that BT isn't particularly interested in maintaining a decent email system so their advise was to move to a gmail or google email which is both fit for purpose and reliably maintained. I have now started to do this and, although it is likely to be a massive pain to get it done, it does also give me the opportunity to move away from BT Broadband which I have paid for for at least the last 20 years (at least) and which I have only kept so that I could use the BT email as I was stupid enough to use a non generic email from the outset. There are cheaper options available.
In summary, BT are not going to change their monitoring of emails so, if you send more than 1 or 2 emails a day, change your email.
