To preview a message, select it from the message list.
A right-click on a message or a folder will display available actions.
Click on a message while holding down the Ctrl key to select multiple messages. To select a range of messages, click the first message of the range, navigate to the last message of the range, and then click on the last message while holding down the Shift key.
The following keyboard shortcuts are available:
/ : Move up/down through the message list.
PgUp / PgDown : Move one page up/down through the message list.
Alt + PgUp / PgDown : Scroll up/down through the display of the previewed message.
Home / End : Move to the beginning/end of the message list.
Del : Delete the currently selected message(s). Shift + Del will delete the current message and move to the next message if a single message is selected.
Shift + N : Move to the next unseen message (non-search folders only).
Enter : Open message in a popup window.
Ctrl + A : Select all messages in the current mailbox.