I\'m designing an app that allows users to email me crash reports if my app ever crashes. I\'d like to leave Mac Mail running on a computer and when an email comes through,
Probably the simplest approach is to define a Mail.app Rule. You can set up filtering conditions to specify the set of incoming email to apply the rule to and among the rule actions you can specify is one to run an AppleScript on incoming messages. Rules are managed with Mail.app Preferences
-> Rules
. Apple supplies examples of Rule Action scripts with Mac OS X. Look in /Library/Scripts/Mail Scripts/Rule Actions
or search the web.
Here's a script that extracts from email into a file using a mail rule: MacScripter / Mail rule script for message export. Might be good for sample code for what you're doing.
Use the Dictionary in Applescript Editor to see the properties of mail and you'll quickly be able to see the properties of any mail message. Here's a quick and dirty example of getting the content of a mail message.
tell application "Mail"
set the_messages to selection
repeat with this_message in the_messages
set mytext to content of this_message
end repeat
end tell
Modify the script linked to above that copies output to a temporary file and then pass that file to your Python script to act on.