Mail delivery failed: returning message to sender

[Mail Delivery System]

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  zstetka na upcmail.cz
    SMTP error from remote mail server after RCPT TO:<zstetka na upcmail.cz>:
    host mxin5.upcmail.net [213.46.255.74]: 550 5.1.1 MXIN500 domain upcmail.cz is not hosted here ;id=IXjbmrEkrSwVFIXjbmNRzY;sid=IXjbmrEkrSwVF;mta=vie01a-pemc-pmxin-pe14;d=20210824;t=164904[CET];ipsrc=62.36.20.208;