mutt showing X-Label header in index view

About a year ago (October 2011), I wrote a small tool (git repo) that has really made using my e-mail a much more enjoyable experience. My personal e-mail inbox is on Google's Gmail service; however, I find the web interface gets in the way of reading and organising my e-mail. I make heavy use of the label and filter features that let me automatically tag each message (or thread), but having labels that number in the hundreds gets unwieldy since I can not easily access them. I use the IMAP interface to reach my inbox through the mutt e-mail client; this is fast because there is almost no interface and I can bind many actions to a couple of keystrokes.

The main problem I had with using IMAP was that, although I could see all the labels presented as IMAP folders, I had no way to know which labels were used on a particular message that was still in my inbox. I had thought about this problem for a while and looked around to see if anyone made proxies for IMAP, but there was not very much information out there. I had originally thought that I would need to keep a periodically updated database of Message-IDs and labels which I would query from inside mutt and I had in fact written some code that would get all the Message-IDs for a particular IMAP folder, but this was a slow process. I didn't look into it again until I was talking about my problem with a friend (Paul DeCarlo) and he pointed me towards the Gmail IMAP extensions. This was actually going to be possible!

I quickly put together a pass-through proxy that would sit between the mutt client and the Gmail IMAP server. Since Gmail's server uses SSL with IMAP (i.e. IMAPS) to encrypt the communication, I would need to get the unencrypted commands from mutt and then encrypt them before sending them to Gmail. Once I had this, I could log the commands to a file and study which IMAP commands mutt was sending. At the same time, I had a window open with IETF RFC3501, the IMAP specification document, so that I could understand the structure of the protocol. Once I saved the log to a file, I didn't actually need a network to program the filter that I was writing — in fact, I finished the core of the program on a drive back from the ACM Programming Contest in Longview, TX! When I got home, I tested it and it worked almost perfectly except for another IMAP command that mutt was sending that was not in my log, but that was just a small fix.

Not very long after I first published the code on Github, my code was mentioned on the mutt developers mailing list on 2012-02-01.

Todd Hoffman writes:

I read the keywords patch description and it definitely sounds useful. One reminder is that gmail labels are not in the headers and can only be accessed using the imap fetch command. Users of offlineimap or some other mechanism to retrieve the messages and put them in mboxes or a maildir structure will not be able to extract them from headers, in general. Of course, a patched version of offlineimap or an imap proxy (see that assigns the labels to a header could be used also.

It was good to know that people were finding my project. Also, over the summer, I received my first ever bug report from Matthias Vallentin, so I knew that somebody else actually found it useful. \o/ This was a great feeling, because it closed the loop on the open-source model for me: I was finally contributing code and interacting with other developers.