Please help me

we can send email to 

one of account in 

chevronindonesia.com

but they said that they 

don't get email from 

admin@dungoreksa.com

When they send email to 

admin@dungoreksa.com from 

their company account 

or from 

chevronindonesia.com ,  

we don't get email from them too

There are no error report 

Please Help me