Is there a way to quickly mark all emails as read instead of going over each one of them manually ?
1. Edit -> Select All
2. Message -> Mark -> As Read
Select all the mails you want using Cmd-click (one by one), Shift-click (a range), or Cmd-A (all in mailbox), then either right-click or Control-click and select
Mark -> As Read. This option is also available through the menu:
Message -> Mark -> As Read. The keyboard shortcut ShiftCmdU will also do the same thing.