Headers

In an e-mail, the text (body) is preceded by header lines indicating sender, recipient, subject, sending time stamp, receiving time stamps of all intermediate and the final mail transfer agents, and much more. (See RFC 2822 for details.) From Wikipedia

Entourage displays newsgroup message headers in the Message list. Although newsgroups can contain thousands of messages, Entourage limits the display to 300 headers by default. You can specify the number of message headers you want to view. If you want to download entire messages and not just the header, check out this rule.

Use a Schedule - such as Send & Receive All to receive news automatically (which receives just the headers) to all your subscribed newsgroups, and also set up a Rule to retrieve all.

The downloaded news messages will still be in the news cache (and will keep showing up in custom views and advanced finds). If you're particularly concerned about the database size, the way to get rid of them is to control-click on the news server icon and select Empty Cache. That empties the cache for ALL newsgroups of the server - but you can just re-download headers and/or messages of newsgroups to which you're still subscribed when you go back to them afterwards. Emptying the cache can speed up Entourage if the database is enormous. It's usually not necessary or advisable to do more than that (the database starts filling up again), but if it's _really_ essential to reclaim disk space, you can do a Typical Rebuild after emptying the cache. That compacts the database.

How does one forward a message with all headers intact?

There are two ways you can send the entire headers.

View -> Source, press Select All, and then Paste the contents into a new message.
Easier way. Philip Kearney of SomeDude Software has produced a script called Forward with All Headers. With this, you simply select the message, press the user-defined keyboard shortcut (preset to Command-Shift-J), and a new message comes up with the entire messages and full headers already pasted in.

How can I request a return receipt from sent mails?

Go to Tools -> Accounts.
Under the Mail tab, edit the mail account you want to send from.
Click the Options tab.
Under "Additional Headers", add in a new header: Disposition-Notification-To
Under Value, type your e-mail address.

f you want your cursor to appear on top and your signature below that (but before the quoted text), select "Use short header-style attribution lines". In Entourage 2001, you can still achieve the same effect using internet-style attribution lines. Download the Reply Insertion Above AppleScript.

http://www.office.mvps.org/faq_topic/reply.html

How can I set a Reply address different than the address I send from?

Go to Tools -> Accounts.
Under the Mail tab, edit the mail account you want to send from.
Click the Options tab.
Under "Additional Headers", add in a new header: Reply-to
Under Value, enter the e-mail address you want recipients to reply to.
Note that this will only be the suggested return address - senders can still choose to contact you from your sending address - for example in Entourage, the Reply command will reply to the default reply address, but the Reply to Sender command will reply to the sending address regardless of whether a Reply-to header is present.

Junk headers

http://www.office.mvps.org/rules/junk/examples.html

Using Search in Entourage

http://www.office.mvps.org/faq_topic/search.html