Gmail automatic message purge

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:

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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