Yes, 543.dk can receive emails.
Yes, 543.dk seems to be a legitimate domain.
A record
None
MX records
alt1.aspmx.l.google.com
64.233.186.26
alt2.aspmx.l.google.com
74.125.193.26
aspmx.l.google.com
173.194.68.27
aspmx2.googlemail.com
64.233.186.26
aspmx3.googlemail.com
74.125.193.27
aspmx4.googlemail.com
66.102.1.27
aspmx5.googlemail.com
173.194.79.26