Putty UTF-8 support from the beginning of authentication

Hello,

I am connecting to my ssh server using Putty, and I would like to send
a banner message with a box drawn using UTF-8 in the range U+2500 to U
+25FF (such as± µ etc... ). It turns out that putty converts any
characters from that range in this character U+2592 ‘ (e2 96 92
MEDIUM SHADE).

Any suggestions?

Thanks in advance