Option to set font for all emails and templates to our standard style and size

We’ve tried changing templates to Arial 10 but when the email goes out it isn’t in Arial 10.

We seem to be spending far too much time fiddling with the font of an email before it goes out to make sure it looks professional.

Clients are already very wary of phishing emails so if we send something out that doesn't match our normal style not only does it look unprofessional but it makes them worried it isn't legit.

It would be great to set a standard for our practice and not have to worry about changing/checking it.