Microsoft (NASDAQ:MSFT) Outlook may be the most widely used e-mail tool on the planet, but it's hardly perfect, which is why enterprising programmers have created a cottage industry in the design of extra features for it. These Outlook add-ons come none too soon for a corporate world that is drowning in information overflow. Research firm IDC estimates that the amount of business e-mail is on track to reach more than six billion gigabytes this year, double the amount sent in 2005. Some of these powerful plug-ins help Outlook better manage these staggering amounts of data. Others help you send huge files, compose bulk e-mails, and even prevent possible humiliation.

Best For Managing Your Contacts

What it is: An add-on that creates a dossier on each of your e-mail contacts

What's Cool: Click on a message, and Xobni displays a profile of the sender. It automatically pulls a telephone number from the signature. Xobni keeps tabs on how much e-mail you send to each other -- including who sends more -- and provides a list of the e-mails and attachments you have swapped. An added bonus for Skype users: Xobni includes a handy click-to-call button. It also includes search.

Drawback: If two contacts have the same name, Xobni can confuse them for the same person.

Price: The program is in beta, and it's free. CEO Jeff Bonforte says it will remain free after the full version launches in early fall, though a premium service may be offered later.

Best For Organizing Outlook Chaos

What it is: Software that sorts your e-mail

What's cool: It scans your inbox and automatically color-codes all tasks, appointments, and e-mails according to the subject matter and how frequently you correspond with the sender. That typically means everything in Outlook having to do with a key client shows up in red, while spam is shaded gray. ClearContext reminds you to follow up on unanswered e-mails from important contacts. In the pro version, you can schedule a meeting from within an e-mail -- a function sorely lacking in Microsoft's original.

Drawback: To get the full benefit of the program, users have to do a certain amount of filing, which detracts from the main intent of the program.

Price: The personal version is free. The pro version costs $89.95, with volume discounts available.

Best For Hunting Through E-mail

What it is: A fast e-mail search tool

What's cool: Tired of Outlook's sluggish search function? This is kind of like having Google (NASDAQ:GOOG) sitting on top of your e-mail. Lookeen indexes everything in Outlook, including your appointments, tasks, and e-mails in your inbox and local folders. That index makes everything easily searchable; results are returned in a fraction of a second, sorted by type. Once you find what you're looking for, you can click a button to bring up all the material associated with that particular name or e-mail thread.

Drawback: Lookeen is a little pricey for what you get, given that the program doesn't offer some of the features that other add-ons offer for free.

Price: $39.80; volume discounts are available for 10 or more users.

Best For Sending Canned Replies

What it is: Software that sends personalized bulk e-mails from Outlook

What's cool: If you find yourself sending the same e-mails over and over -- such as answers to frequently asked questions -- Email Templates can speed up the process. It helps you create customized messages that are instantly available from a pull-down menu in Outlook. Replies are automatically populated with information, such as a name and e-mail address, from the incoming message.

Drawbacks: Email Templates may not be worth the time and effort unless you have a job that deals with truly huge volumes of e-mail. And if you forget to fill in one of the blanks, the recipient will know that your personal note isn't so personal.

Price: Free for a very limited, stripped-down version; $99 for the pro version

Best For Avoiding Reply-to-All Gaffes

What it is: An add-on that keeps you from accidentally sending a group reply

What's cool: Ever tried to make a private remark over e-mail and mistakenly replied to the whole organization? This little plug-in could have saved you. When you click the Reply to All button and hit Send, it pops up an alert box that basically says, Hey, are you sure you want to do that? It can also give you a heads-up when you are about to lose your anonymity by replying to an e-mail on which you were bcc'd.

Drawback: You don't get many features. The maker of this program, Sperry Software, has created several helpful Outlook add-ons, but it sells them individually instead of in one bundled suite.

Price: $14.95

Best For Sending Big Files

What it is: A virtual drop box for sending and receiving attachments of up to 2GB

What's cool: Most e-mail systems don't let you send files that are bigger than a few megabytes. And even when big files can be sent, you can't count on them being received. YouSendIt fixes that. Install its plug-in, and when you send a large attached file in Outlook, recipients get a small e-mail containing a link to a site from which they can download the file. You can tell YouSendIt to step in only when your attachments exceed a certain size.

Drawback: If you are sending sensitive documents, you will need to spring for the $29.99-a-month version, which password-protects the files.

Price: You can send attachments of up to 100MB each for free. Plans that allow you to send files up to 2GB in size start at $9.99 per month and go up when you add users and features.