Splitting a GMail mbox File by Label

There are often times that it is necessary to backup your gmail mail and import the resulting mbox file into your favorite email client. I use Mozilla Thunderbird as a powerful, yet free, email client. However, the mbox file that is exported by gmail is flat – all email from the gmail account are put into one mbox file. Writing a Thunderbird extension was quickly becoming too tedious. (The developer documentation is the worst documentation I have seen! But that is a rant for another time.) So, I decided to write a simple python script to split the mbox file into separate files for each label. It is not perfect (an email in gmail can have multiple labels but will only exist in one mbox file).

Without further ado, here is the script:

import sys
import getopt
import mailbox

def main(argv):
	in_mbox = "MikeBackupInbox.mbox"
	prefix = "MikeBackup"
	try:
		opts, args = getopt.getopt(argv, "i:p:", ["infile=", "prefix="])
	except getopt.GetoptError:
		print("python splitgmail.py -i  -p ")
		sys.exit(2)

	for opt, arg in opts:
		if opt in ("-i", "--infile"):
			in_mbox = arg
		elif opt in ("-p", "--prefix"):
			prefix = arg
	print("Processing file - " +in_mbox+" with prefix = "+prefix)
	boxes = {"inbox": mailbox.mbox(prefix+"Inbox.mbox", None, True), "sent": mailbox.mbox(prefix+"Sent.mbox", None, True),"archive":mailbox.mbox(prefix+"Archive.mbox", None, True)}

	for message in mailbox.mbox(in_mbox):
		gmail_labels = message["X-Gmail-Labels"]       # Could possibly be None.
		if not gmail_labels:
			boxes["archive"].add(message)
			continue
		gmail_labels = gmail_labels.lower()
		if "spam" in gmail_labels:
			continue
		elif "inbox" in gmail_labels:
			boxes["inbox"].add(message)
		elif "sent" in gmail_labels:
			boxes["sent"].add(message)
		else:
			saved = False
			for label in gmail_labels.split(','):
				if label != "important" and label != "unread" and label != "starred":
					box_name = prefix+label.title()+".mbox"
					if box_name not in boxes:
						boxes[box_name] = mailbox.mbox(box_name, None, True)
					boxes[box_name].add(message)
					saved = True
					break
			if not saved:
				boxes["archive"].add(message)

if __name__ == "__main__":
    main(sys.argv[1:])