Swift_Mailer + symfony UTF-8

Question

I have an issue with Swift_Mailer in Symfony. I am sending e-mail messages in French which contain a lot of "à é è" characters. At first when i tried sending these characters came out fine in my email-client, but in my colleague's email-client they didn't.

So I put the text for the mail through a utf8_encode function and tried again. Now it is vica-versa. It shows fine in my email-client, but screwed up in my colleague's.

What is the best way to solve these e-mail UTF-8 issues with Swift_Mailer in Symfony?