Trouble setting up email

I setup a new account today i have also the same issue
my subdomain is so mx is set to

but on top of my subdomain is this domain visible

normaly is already each subdomain or primedomain is setup mx record,but this account i really missunderstand the config.
question who is and can i delete it without issue ???

why i can’t login to webmail its always tell me wrong password,even if setup new password for email account
,whats wrong with my setup

if you busy with your work please don’t do instead of rude to newbies here

BTW idin’t want ( Can you please create your own topic instead of hijacking this one? )