Change Viewing preferences in Mail on Mac
Use Viewing preferences in Mail to change options for viewing messages.
To change these preferences in the Mail app on your Mac, choose Mail > Preferences, then click Viewing.
The number of lines of the message to show in the message list.
Move discarded messages into
This setting also determines whether you can delete or archive messages from Mail notifications.
Show message headers
Show default or custom fields in message headers.
To add fields, click the pop-up menu, choose Custom, click the Add button , then enter the name of a message header, such as Return-Path.
Display unread messages with bold font
In column layout, show unread messages in bold to help distinguish them from messages you have read.
Load remote content in messages
When remote content is retrieved from a server, information about your Mac can be revealed. You can deselect the option for increased security, but some messages may not display correctly.
Remote content isn’t displayed in messages that Mail marks as junk.
Use Smart Addresses
Show recipients’ names but not their email addresses (if a recipient is in the Contacts app or the Previous Recipients list, or on a network server).
Use dark backgrounds for messages
Show messages in the preview area and new messages you’re writing with a dark background (when this option is selected) or a light background (when this option isn’t selected). This option is available only if you selected the Dark appearance in General System Preferences.
When this option is selected, you can switch to a light background while viewing or writing a message. Choose View > Message > Show with Light Background. To see the message with a dark background again, choose View > Message > Show with Dark Background.
Highlight messages with colour when not grouped
When conversations are turned off, highlight the messages in a conversation in the message list, to help identify them more easily. Click the colour well to choose a highlight colour.
Include related messages
Include related messages (those located in other mailboxes) when viewing a conversation.
Mark all messages as read when opening a conversation
Mark all unread messages in a conversation as read when you view the primary message of the conversation.
Show most recent message at the top
Display the most recent message in a conversation first in the preview area. If deselected, the oldest message appears first.
You can sort, filter and otherwise change how messages appear in the message list.