The Bank Of England is the central bank of the United Kingdom and the model on which most modern central banks have been based. It was established in 1694 and so for the large majority of its operation has not had to worry about email.
Earlier this week, the bank confirmed it is researching the financial risks of the UK leaving the EU after it "inadvertently" sent details of its work to a national newspaper. We have all done this at some point or another, although probably not with the same level of sovereign financial risk as the hapless individual at the “Old Lady Of Threadneedle Street” as the bank was affectionately referred to in days gone by.
However, had the Bank been running Apple computers and using Apple’s Mail application there is a simple preference that could have been used to avoid this kind of mishap.
There is a feature that in the Mail preferences panel that allows you to instruct Mail to highlight in red any “unsafe” email addresses. As Apple’s support pages state:
That said, I suspect it is unlikely that the Bank is running any Macs in their office, save perhaps by the web designers.