This is by design from Apple
If this is not to the user's liking, use a Third Party email Client that better suits there wants and needs
Change Privacy preferences in Mail on Mac
Use Privacy preferences in Mail to manage settings that prevent email senders from learning your IP address and information about your Mail activity.
To change these preferences in the Mail app 
on your Mac, choose Mail > Preferences, then click Privacy.
Option
Description
Protect Mail Activity
Hide your IP address from senders and privately download remote content in the background when a message is received (instead of when you view it). This option prevents senders from collecting information when you view a message, such as when and how many times you view it, whether you forward it, your IP address, and other data.
If you deselect this option, you can choose to separately hide your IP address and prevent remote content in a message from being downloaded until you choose to do so.
Hide IP Address
Hide your IP address from senders. This option is automatically selected when Protect Mail Activity is selected.
If you deselect Protect Mail Activity, it’s recommended that you keep this option selected, to prevent senders from learning your IP address.
Block All Remote Content
Indicate when a message contains remote content and prevent it from being downloaded until you choose to do so. If you deselect Protect Mail Activity, it’s recommended that you select this option.
Remote content is never displayed in messages that are marked as junk.
Note: If you deselect the checkbox in Network preferences to limit IP address tracking for your Wi-Fi or Ethernet network, your IP address isn’t hidden from senders when using the network.
