Three years ago—has it really been that long?—I reviewed Mail Act-On 1.3.1, a handy plug-in for Mail that let you invoke mail rules using the keyboard. This meant that anything you could do with a rule in Mail—move, copy, forward, redirect, reply to, or delete a message; set the color or read/flagged status of a message; or even run an AppleScript—you could do via the keyboard using Mail Act-On.

Earlier this year, I briefly mentioned a beta version of Mail Act-On, 1.3.3b, that provided preliminary Leopard compatibility. But the developer, Indev Software, has recently released Mail Act-On 2.0.1, and this major upgrade warrants a full review, as it adds many new features and makes Mail Act-On a required add-on for many Mac users.

Like the original version, Mail Act-On 2 lets you apply specific rules to selected messages at any time—in other words, only the rule(s) you want to apply, whenever you want to apply them—via simple keyboard shortcuts. After selecting one or more messages in Mail, bringing up Mail Act-On’s rules menu (accessed via F2, by default) shows any rules you’ve created. Press the shortcut key for the desired rule (or click on the rule name with your mouse, or use the arrow and return keys to choose the rule), and the rule is applied to the selected messages. Because these are rules, their actions apply only to those messages that fit the particular criteria you’ve defined.

Once you’ve used Mail Act-On for more than a few minutes, this process becomes second nature. And you don’t need complex rules to get good use out of Mail Act-On; I regularly use it just to move messages to particular folders (mailboxes in Mail parlance). For example, I have a rule for moving email to my Family folder; whenever I receive a family-related message I want to keep, I quickly invoke that rule and the message is moved to the Family folder without me ever touching the mouse.

You can also apply any rule without having to bring up the Mail Act-On menu by adding the control key to the rule’s shortcut. And if you regularly apply multiple rules to messages, a new feature in version 2 lets you lock the menu window so that it stays open, allowing you to quickly apply rules in succession. Another welcome new feature is the capability to undo rule actions; if you realize you’ve applied the wrong rule to a message, just choose Mail’s Edit: Undo command to reset the affected messages back to their original states (and, if a rule moved them, to their original locations). Unfortunately, in my testing the Undo command was unavailable when I moved mail from an IMAP (remote) folder to a mail folder on my computer; the developer is looking into this issue.

Among heavy users of email, perhaps the most popular new feature of Mail Act—and one that gives Mail a bit more parity with Microsoft’s Entourage—is Outbox Rules, which allow you to apply rules to messages as you send them. For example, if you use Mail for both work and personal email, Mail Act-On can automatically file any outgoing email sent from your work account into a Work Sent folder.

Mail Act-On 2 also makes it much simpler to configure rules. Under older versions, because Mail had only a single list of rules, you had to name Mail Act-On rules using a very specific format to differentiate them from standard rules (and to indicate the keystrokes for invoking them). In version 2, Mail Act-On actually modifies the Rules screen in Mail’s Preferences dialog, dividing it into Inbox Rules (Mail’s standard rules), Outbox Rules, and Keystroke Rules; the dialog for each Keystroke Rule now provides a field for choosing its keystroke.

(Tip: If you regularly need to perform several actions on the same message[s], but you can’t include all those actions in a single rule—or if you want the message[s] to be compared against several distinct sets of criteria—you can create multiple keystroke rules and assign them to the same keystroke. When you press that keystroke, Mail Act-On will apply all those rules to the message[s].)

My personal favorite among Mail Act-On 2’s new features is the ability to quickly move messages to a particular folder, even if you haven’t defined a rule for this task. Much like MsgFiler, Mail Act-On lets you press a keyboard shortcut (by default, F3) and then type the first few letters of the desired folder name. Assuming those letters are enough to identify the desired folder, you simply press return to move the selected message(s) to that folder; if more than one folder matches, you can type more letters to narrow down the choices, or you can use the arrow keys to choose the folder manually. If you’ve got lots of subfolders, Mail Act-On provides several shortcuts for quickly navigating your folder hierarchy. Similarly, you can press option-F3 (by default) to copy selected messages to a folder.

For both the move and copy features, the most-recent folders are displayed at the top of the list for easy access, each with a numeric keyboard shortcut; for example, 1 for the most-recently-accessed folder. When reading your email, there’s also a feature (shift+F3, by default) for quickly switching to a different folder.

If you’d rather not have to remember these various menu shortcuts, you can instead use Mail Act-On’s main menu, accessible by pressing F1, which gives you quick access to all feature-specific menus.

Whenever you perform an action, Mail Act-On displays a small, floating confirmation message that fades away after a length of time of your choosing. You can also choose the keyboard shortcuts for accessing Mail Act-On’s menus, as well as the sort order of Keystroke Rules. These settings are located in a new screen in Mail’s Preferences dialog.

Mail Act-On 2’s performance is also much improved compared to older versions, and it now integrates with the developer’s own MailTags, which lets you tag messages with keywords or categories that are Spotlight-searchable, as well as add notes, priorities, and due dates to messages. With MailTags installed, MailTag’s Add Keyword command and other actions appear in the main Mail Act-On menu for quick access.

If you’re a power user of Mail, or someone who just prefers pressing a few keys to mousing all over the screen, Mail Act-On 2 is a must-have. Unlike older versions, Mail Act-On 2 isn’t free, but if you spend a lot of time in Mail, $20 is a paltry fee for the increase in productivity—and the reduction in mousing strain—this add-on brings.