At the request of MacSparky, I've put together a few AppleScripts for Mac Mail users, to mark messages as read...

Script 1: Mail • Mark All Inbox Messages Read

tell application "Mail"
     set read status of every message of inbox to true
end tell

Script 2: Mail • Mark All Messages Read

display alert "Please note!" message "This script may take a while if you have a ton of mailboxes. Do you want to continue?" buttons {"Cancel", "Yes"} cancel button "Cancel"

with timeout of  600 seconds
     tell application "Mail"
          set read status of every message of inbox where its read status = false to true
          set read status of every message of every ¬
               mailbox where its read status = false to true
          set read status of every message of every mailbox ¬
               of every account where its read status = false to true
     end tell
end timeout

Script 3: Mail • Mark Selected Mailbox Messages Read

display alert "Please note!" message "This script may take a while if you have a lot of mailboxes selected. Do you want to continue?" buttons {"Cancel", "Yes"} cancel button "Cancel"

set processSubMailboxes to (button returned of (display alert "Would you like to scan all submailboxes too?" message "Again, if you have a lot of selected mailboxes and submailboxes, this may take a while." buttons {"Yes", "No"})) = "Yes"

tell application "Mail"
     tell front message viewer
          set theSelectedMailboxes to selected mailboxes
          repeat with a from 1 to length of theSelectedMailboxes
               set theCurrentMailbox to item a of theSelectedMailboxes
               processMailbox(theCurrentMailbox, processSubMailboxes) of me
          end repeat
     end tell
end tell

on processMailbox(theMailbox, processSubMailboxes)
     tell application "Mail"
          if processSubMailboxes = true then
               set theSubMailboxes to every mailbox of theMailbox
               repeat with a from 1 to length of theSubMailboxes
                    set theCurrentSubMailbox to item a of theSubMailboxes
                    processMailbox(theCurrentSubMailbox, processSubMailboxes) of me
               end repeat
          end if
          set read status of every message of theMailbox to true
     end tell
end processMailbox

Usage

You can download these scripts here.

You can quickly and easily run them from the system-wide AppleScript menu.  This menu is not enabled by default.  To enable it and install the scripts...

1. Launch AppleScript Editor in /Applications/Utilities
2. Select AppleScript Editor > Preferences from the menu bar
3. Under General, click the Show Script Menu in the Menu Bar checkbox
4. Bring Mail to the front
5. From the script menu, choose Open Scripts Folder > Open Mail Scripts Folder
6. Copy the scripts into the folder.  They will now be available from the script menu when you're working in Mail

Enjoy!

-Ben

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