utf8 domains and emails

[monstermedia]

Hi.

We got some problem with domains(polish diactric signs) such as:

edgar@słoma.com.pl
or
mila@świetnadomena.pl

When try to send to such domains we got message from server:

5.1.3 bad recipient address syntax

So... we can hold such domains with Ispcp... but we cannot use emails with them? We need change configuration of smtp or something?
How to workaround it? Thanks in advance

Regards
Piotr Mąsior