For example, the HelioHost server is hosting the domain named "example.com". And the e-mail "report@example.com" under that domain name is handled by other popular mail server, as the MX record of "example.com" is mail handled by this mail server. When I use the other email, for example as "mail@other.com" to receive an email from "example.com", this email can recieve a mail from it. But why the email "report@example.com" couldn't receive a mail from the server of "example.com"? I also try to receive a mail using the other email that is handled by the mail server that's the same as the mail server of "example.com" and it's still recieving email from the domain.