a. Plesk 9.2.1 - DomainKey working
b. Install SpamAssasin - DomainKey broken
c. Change MTA to qmail - DomainKey working again
d. I am afraid to update to 9.2.2
go figure... and I am not talking about DKIM, it just doesn't exist.
DKIM has to be implemented into Plesk. Gmail checks only...