From address showing hostname of the system

From address showing hostname instead of domain name. Actually the domain name was trans-world.org but it showing hostname of the system. Can you please suggest whats wrong here.

For eg. see below mail:

From
“Heather” heather.trans-world@usa.official.shared-hosting-server.host-space.org Find email with same senderCreate filter by sender
To
mohiddin-shaikh@trans-world.org Find email with recipientCreate filter by recipient
Date 10/01/2017 15:25
Subject