MessageLock for Outlook 2003   
http://www.encryptomatic.com

Your private email message are not so private. When attached to an email, your files (pictures, documents, videos, etc) and message may as well be printed on a postcard as they travel across the internet to their intended recipient. History has proven that unsecured messages can be intercepted, redistributed, published, and tampered with, sometimes with serious consequences. Introducing MessageLock(TM) by Encryptomatic llc - Quite possibly the world's easiest to use sender-to-recipient email security solution. MessageLock provides 1-click encryption of email messages and attachments within Microsoft Outlook, combining strong U.S. Gov't approved AES-256 bit encryption with the nearly universal compatibility of the Zip file utlity. MessageLock delivers encryption and compression for your message and/or file attachments, protecting your data while it is traveling across your intranet and the internet. MessageLock gives you a choice of encryption methods, from super-strong AES-256 bit, to AES-128 bit, and the weak but highly compatible Zip-2.0 algorithm. To use MessageLock, all you do is associate an email address with a password, a process that takes just seconds. Or, just go ahead and send an encrypted email -- if MessageLock can't find the password to use, it will ask you for a password and then remember it for the next you send to this email address. If MessageLock is installed at receivers end, the message can be decrypted immediately upon receipt and displayed as a regular message. The only difference is a single line of text at the bottom of the message that alerts the reader that this message was transmitted securely. If the receiver does not have MessageLock, they can still decrypt the zip file if they have the password, and any zip utility that supports the encryption method used. WinZip 10.0 or the free TugZip utility can both decrypt AES-256. Download a fully functional trial and see how easy MessageLock is to use.

EM Antiblock   
http://www.engelmann.com

By default, Microsoft Outlook will prevent you from opening certain file attachments that can damage your computer, e.g. by containing malware code. However, sometimes you need to be able to handle these attachments. EM Antiblock offers you the ability to easily decide which file attachments you can trust, by managing the file extensions for the blocked attachments. And the best of all: This software is freeware! Compatible with Outlook 2000 to 2003.

SharePoint Attachements   
http://www.kalmstrom.nu

Outlook can be configured to publish files directly to a SharePoint site instead of sending the file as an attachement. This allows you to make better use of your intranet and your Exchange server. Outlook is good for a lot of things, but not for file transfers. Works with any Frontpage or WebDAV site but of course best with SharePoint document libraries. Free 15 day trial and a low price tag of only 25 US$.