mail forwarding loop for sample.email@firstdomain.com

[admin2]

Hi there,

I am getting error messages for mail sent to 
sample.em...@firstdomain.com but in the /etc/postfix/aliases file I have 
an entry for sample.email to send to sample.em...@anotherdomain.com . 
why am I getting a forwarding loop.

Status: 5.4.6
Diagnostic-Code: X-Postfix; mail forwarding loop for 
sample.em...@firstdomain.com



r...@firstdomain.com:/etc/postfix# cat /etc/hosts
127.0.0.1     localhost localhost.localdomain
174.143.253.66     firstdomain.com

# cat /etc/mailname
firstdomain.com


Please help.

Cheers,

Noah