Sending e-mails to Seznam.cz

Sending e-mails to Seznam.cz

Hello,
I just set up an accound for business email with Zoho.com and everything seems working but sending e-mails to provider Seznam.cz (I tried multiple e-mail addresses there and none of them recived any e-mail; plus on Zoho I received MailerDamon notice; on the contrary sending e-mails to Gmail works just fine and quick). My question is if the problem is on your Zoho.com side or on the Seznam.cz side? And is there something that can be done to make it work?
Best regards, Jana