it doesn't matter... let's see MX (dns) record for that domain:
[slwkk@slawcio ~]$ host -t mx autograf.pl autograf.pl mail is handled by 2 mx.poczta.onet.pl. [slwkk@slawcio ~]$
As you see this domain is handled by mx.poczta.onet.pl mail server... now it's pretty easy to get poczta.onet.pl and here you are, they allow you to register mail account in following domains: