MailTags -- How I did it

[Scott Morrison]

Hello all -- and thanks for inviting me.

I have glanced at the archives and thought it best to start with some  
of the decisions I made.

There has been some debate about using IMAP flags.

I don't really use IMAP flags.  Here are a few of my reasons
	1) Not all servers support them or the support is limited. And  
trying to explain to end users that their server is limited in its  
capabilities is not something I want to do.
	2) They can be volatile -- I have seen servers whack all the IMAP  
flags when moving messages to different IMAP folders.
	3) They don't persist if you decide to archive the email offline
	4) They are limited in the form of data -- single word, cannot deal  
with notes, times, can't differentiate between keywords and  
categories, and priorities etc.
	5) Can not share tags (ie send them) to others.

My method of tagging is to save the data in a X-Mailtags header.  The  
data dictionary is encoded as JSON structure which is a very  
lightweight alternative to xml .  I also give the option of storing  
keywords and projects as X-keywords and X-project headers.

The advantage of this is that
	All servers should be able to handle it.
	When you archive messages offline - the tags are there
	Procmail can add tags if it needs to -- I have a couple of users  
that do exactly this -- using proc mail to provide pretty powerful  
tagging before the mail even gets to the client.
	Tags can be almost anything, and they can be sent to others for  
sharing a workflow.

What I do is create a new message with the Tag data embedded, write  
it to the server with an APPEND command, and then upon success,  
delete  and expunge the old message.    The downside is that it can  
be bandwidth heavy -- especially for large (attachments included)  
messages.   However, my analysis show that this is pretty much how  
drafts are handled with IMAP server and Mail.app at least. and most  
people have good bandwidth these days -- especially if they are using  
IMAP.

I do use IMAP flags (when available) as a token system to keep track  
of which clients have seen the tags.  Basically this works by adding  
a token to a message when it is tagged or viewed.  The client can  
then find any freshly tagged messages with a Search  where Headers  
include X-MailTags and keyword (IMAP flags) != token.

My biggest issues have not been dealing with the IMAP server but UI  
issues on the client --- dealing with things like replacing the old  
(untagged) message with the new tagged message in the local cache,  
changes to tags on a message before the update is complete.

But then again, the list is not about working with the UI problems.  
but devising a standard that can be used.

I would actually welcome work on a thunderbird tagging (not tag the  
bird!) extension or one for outlook that made use of MailTags  
formated headers.

Scott




	

________________________________
Scott Morrison <smorr at indev.ca>
Creator of Mail Act-On and Mail Tags plug-ins for OS X Mail.app.    
<http://www.indev.ca/>