Not receiving emails from one specific domain

Hi,

I'm having problems with not receiving emails from one specific domain @youmail.dk. It hasn't been an issue earlier, but I stopped receiving the emails late last year. For all I know this is the only domain there's a problem with - I don't have any problems with any other random domain.

There is no rules or anything like that set up, so I have no idea what the problem could be... There's no "failure to deliver" notification send to the sender either.

It doesn't matter if I check iCloud online, on my MacBook or iPhone...

Can anyone help me?

Nina.