Alexander wrote:

Hi, I''m trying Outlook (2007) for the first time. Surprisingly, I
can't seem to figure out how to mark a message as junk. There is a
menu item for marking a message as NOT junk, but how do I mark it as
junk?

You don't. Outlook's junk mail filter is not user-trainable. Your choices
for controlling the junk e-mail filter can be found on ActionsJunk
E-mailJunk E-mail Options.

My second question is how to make outlook automcatically retrieve
mail from servers but not at the same time send messages that are
currently in the outbox. Generally, I want to receive automatically
but never send automatically.

Click ToolsSend/ReceiveSend/Receive Settings?Define Send/Receive Groups.
Select your Send/Receive group (usually "All Accounts") and click Edit.
Select each of your accounts and uncheck the "Send mail items" box.

And a third question: I'm used to receive notifications about calendar
entries via email. Is there a way to make outlook send me a mail
notification instead of popping up a window on the desktop? The
reason is that I'm looking at my mail frequently but a popup is gone
once dismissed, so I forget...

Outlook's reminders (without any third-party add-ins) are pop-up reminders.
I don't believe it can mail you a reminder. Your solution, however, is
simple: don't dismiss the reminder until you've addressed the calednar
event.
--
Brian Tillman