[Mailman-Users] Problem with Farsi characters

[Javad Hoseini]

Hi there everybody
In my mailman administration control panel, I tried to add some Farsi text to the welcome message, because mailman does not have any 
Farsi interface. I added something like this:
خوش آمدید.

But mailman sends only some peculiar numbers and letters instead of Farsi text. It writes something like this in the beginning of 
welcome email:
29 at 592&625&2wfo

Why is that? How can I solve this?