Probably test this out internally, it worked for me just a few moments ago.
Lets assume the common email address shared by Joan and John is johan@gmail.com
Create a new contact record for Joan with email: johan@gmail.com
Create a new contact record for John with email: johan+1@gmail.com
Despite the +1 in John’s email, the email will infact be sent to johan@gmail.com. Hubspot/gmail tends to disregard the +postfix in the email.
So now any email sent by johan+1@gmail.com would actually be sent with John’s name and not Joan.
Hope this made sense? Give it a shot and see if it works for you 