Firstly, (while I think hard about why), let me reassure you that you were quite correct when you wrote, "You have sent it to the wrong person."
There are two particular, specific people involved, you and Michael.
His friend Michael is the right person - the particular, specific person he calls 'my friend Michael', and the intended recipient.
Inadvertently, it has gone to the second specific person - you - who, compared with his friend Michael, is hence specifically the wrong person to have received his email.
- For Teachers