For this kind of professionnal use of E-mail, I abandonned
Mail many years ago.
Thunderbird ( Thunderbird home page ) which is much more secure, lets you configure it exactly the way you are looking for through the concept of "identities". You can define many "identities" per account, each one being defined by:
- a name
- a "From:" field
- a "Reply-To:" field
- an "Organization:" field
- a signature (in HTML or text)
I use this E-mail client as a much faster interface to
Gmail letting me answer with the identity required and permitting my correspondant to answer me with my appropriate reply address.
As a collateral advantage, you will most probably discover many other advanced function to use in