It would be nice to decide who I am writing using which identity. This add-on checks the list of recipients before sending a message and displays a warning if the outbound email address or domain does not match your needs. In addition, it is possible to correct the mistake automatically (if it is allowed).
Let the correspondence will be calm and pleasant ! :)
P.S. Source code available here: https://github.com/snakelizzard/flexible_identity