Change "Content-Type" in email header generated by RT

RT Users
1

Hi,

RT generates emails with “Content-Type: text/plain” in header. How can
I change this to something like
"Content-Type: text/plain; charset=iso-8859-1" and
"Content-Transfer-Encoding: 8bit"?

Then, my email client would display umlauts ‘���’ correctly.

Hajo