Gmail automatic message purge

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I've been running an AppleScript to automatically purge messages in specific IMAP folders (aka "labels") for quite some time. This approach works most of the time, but really puts a heck of a load on the Apple Mail client and makes the interface effectively unusable while the script goes through the motions. This wasn't a problem when the script finished in a few seconds. However, it now takes several minutes; not good. Also, the AppleScript assumes a blanket expiry age for all IMAP folders. Want one folder with a different expiry? Too bad. So with the interface problems and lack of flexibility, I decided to smash something out this morning using Google Apps Scripting.

I had some simple requirements for my new server-side script:

  • Must run when I'm off-line
  • Don't delete unread messages/threads
  • Allow fine-grain, per-label expiry age (in days)
  • Keep a plain text log file in my Google Drive.

Behold! I offer the following, which achieves all the above requirements and is triggered to run every 30 minutes:

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function cleanUp() {
        var myLabels = {
                // "Path/to/label":DAYS,
                // Where DAYS is the number of days to keep read messages.  Unread messages aren't touched.
                "INBOX/Mail Lists/CERT":14,
                "INBOX/Mail Lists/Nikola":7,
                // Keep going with any/all labels you want to be automatically purged :)
                "INBOX/System Messages/Router":14,
                "INBOX/System Messages/Web Site":7
        }

        // Iterate over folders and see if there is anything we need to do...
        for (myKey in myLabels) {
                var label = GmailApp.getUserLabelByName(myKey);
                var days = myLabels[myKey];

                // Make sure we have a valid expiry window
                if ( days > 0 ) {
                        // Calculate an absolute date/time to purge messages older than...
                        var maxDate = new Date();
                        maxDate.setDate(maxDate.getDate()-days);
                        var threads = label.getThreads();

                        // Counter to log how many message are purged.
                        var deleted = 0;

                        // Log what we're about to do...
                        Logger.log("Purging '" + label.getName() + "' older than " + days + " days (" + maxDate +")" );

                        // Iterate over the messages in the managed folder
                        for (var i = 0; i < threads.length; i++) {
                                // Is this message old enough to purge?
                                if (threads[i].getLastMessageDate()<maxDate) {
                                        // It's old enough, but is it unread?
                                        if (!threads[i].isUnread()) {
                                                threads[i].moveToTrash();  // Purge this message: it's old enough and marked "read".
                                                deleted++;                 // Increment deleted message counter.
                                        }
                                }
                        }

                        // Only log a message if we did something
                        if ( deleted > 0 ) {
                                Logger.log("Deleted " + deleted + " messages from \"" + label.getName() + "\"");
                        }
                }
        }

        // The results to the log file
        logFile();
};

function logFile() {
        var LogFile = "mail-purge.log";
        var rootFolder = DocsList.getRootFolder();
        var logs = rootFolder.find(LogFile);
        var thisLog = logs[0]; // Assume the best...we'll confirm next.

        if(logs.length == 0){
                Logger.log("Creating new log file")
                thisLog = DocsList.createFile(LogFile, "New log file");
        } else {
                // The find call found "something" - let's get the correct index
                for (var i in logs) {
                        if ( logs[i].getName() == LogFile ) {
                                // Found the correct file!
                                thisLog=logs[i];
                        }
                }
                Logger.log("Found existing log file " + thisLog.getName());
        }

        thisLog.append(Logger.getLog());
};

I think it's pretty self explanatory. The mechanisms for creating the script and firing it with time-based triggers I'll leave for a exercise for the reader. If you really get stuck, drop a comment below and I'll see if I can help :) Happy scripting folks!

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