I have a verizon isp account that will send mail to an account I created.

I have 2 different webserver accounts that can not send mail to same account.

1 has error: Sorry, I couldn't find a mail exchanger or IP address. (#5.4.4)

The other error:550 5.1.2 <rick@domain.com>... Host unknown (Name server: domain.com.domain.com.: host not found)
not sure why domain is repeated twice in the 2nd example.

This problem occures on all accounts created with an assigned IP address. Main account works fine
Could this be a reverse DNS issue?