On certain Outlook versions and by default Deleted items can appear as grayed out or with a strike-through when you delete them. This is typical behavior that is called Purging. Messages marked for deletion are executed when the folder gets purged. The work around to seeing messages marked for deletion with a strike through is to hide them and let them get deleted in the background without seeing them again.
Here's how to configure Outlook to hide deleted messages from IMAP folders rather than showing them with a line through the text:
- Open the folder where you want to hide strike-through messages, like your Inbox folder.
- Go into the view ribbon menu. older Outlook versions: View > Arrange By.
- Choose the button called Change View (2013 and up) or Current View (2007 and 2003).
- Select the option called Hide Messages Marked for Deletion.
In some versions of Outlook, this same menu lets you select Apply Current View to Other Mail Folders... if you want this change to work with your other email folders and sub-folders.
Note: If the preview pane is turned off during this change, you can re-enable it through View > Reading Pane