I'm working on a revamped proposal and I have a few queries : 1. One of the essential features is downloading mail headers only. I need some advice on how this would work. Consider the following: Mail header is downloaded as a file with attributes as usual, but the file contains only the Sender , The subject and the date. the natural question now is how would the user ask for the full message to be downloaded? Will a tracker-addon be sufficient? so that you simply right-click the message and you get an option to download the whole message? 2. Query support : I want the emails to be query-able in much the same way they are now? Does adding query support require anything special? AFAIK, if I make all the query-able entities file attrbutes then queries should work. Is that right? 3. Cacheing : the big question is - how much mailbox data should we save on disk? Currently atleast the headers of every mail that has not been deleted will be saved. Of course the user can be given options so that mails before a particular time are not stored on disk. I read some discussions on the topic of mails and discovered that some users want the Filesystem to be a virtual reflection of their IMAP accounts. The question now is when should the mails be retrieved? 4. Deletion : Based on how Gmail and other clients such as Thunderbird work, the /Deleted flag looks like bad news. So this is how I propose deletion should work- When the user deletes a mail, it is moved to trash folder on his FS as well as his server. To remove the mail completely, goto your trash folder and delete the mail from there, it will be removed from your computer as well as the server. If a user wants to empty the cache on his computer, he can do so. The FS will get mails recieved after the last cache-empty event. The user can also archive certain mails, so that they remain permanently on his archive(The archived mails are not touched on the server, they only stored in a seperate folder on the user's computer) until of course the users deletes them from the archive after which they behave like normal deleted mails.