View deleted emails in Mail on Mac
Depending on how you set options in Mail settings, you can view and retrieve messages after you delete them.
Go to the Mail app on your Mac.
Choose Mail > Settings, then click Accounts.
Select an account, click Mailbox Behaviors, then check the setting for the Trash Mailbox option.
If a mailbox is specified: You can view deleted messages in the Trash mailbox until they’re permanently erased. To retrieve a deleted message, drag it from the Trash mailbox to another mailbox.
If None is specified: Deleted messages are removed and aren’t available in the Trash mailbox.
Tip: If you mistakenly delete messages, just drag them out of the Trash mailbox to another mailbox. Or select them in the Trash mailbox, then choose Message > Move to > [mailbox].
Deleted messages are available until they’re permanently erased.