When considering importing emails into your DEVONthink databases, the question of "automatic" email importing invariably comes up. While this isn't fully possible yet, there is a mechanism in Apple Mail that can provide some level of "automatic": Mail Rules.
Found in Apple Mail's Settings > Rules, these are a rules consisting of criteria to be matched and an associated action (similar to smart rules). As incoming emails are detected, Mail will check for matches in a rule and execute any actions you've specified in the rule.
One of the actions available is Run AppleScript. Selecting this option shows a dropdown with any installed Mail Rule scripts. These scripts are installed in ~/Library/Application Scripts/com.apple.mail folder. If you write or obtain other scripts for use with Mail Rules, they can also be placed in this directory. The scripts provided by DEVONthink are:
A full lesson on writing scripts for Mail Rules is beyond the scope of this help, but you can open and explore the installed scripts.
Do note there are two required handlers: using terms from application "Mail" and on perform mail action with messages theMessages for rule theRule, where theMessages is a variable representing the items matched by the rule. Here's a simple example: