IMAP: download only headers

[brecht]

The user should be able to specify that only messages' headers are fetched. The full message should be fetched on reading a message.

[ithamar]

The problem with this approach is that it requires modifications on the email _client_ side. Currently, mail is stored as plain text files, with many headers 'exported' as attributes. We would have to add an attribute to the file to specify that it is header-only, and that the rest of the mail should be retrieved.

Also, normally the connectivity to the mail server is handled by the mail_daemon.

So to sum up the changes required:

• Add attribute to 'standard' mail format signalling email content needs to be retrieved.
• Update Mail Kit API to include accessor for this attribute and method to 'update' mail (?)
• Interface between Mail Kit API and mail_daemon to actually contact mail server and retrieve body.
• Update BeMail to include the check for headers-only mail files.

Anybody any comments?

[axeld]

Nathan implemented IMAP support, but I could have sworn MDR already supports that feature; I never used IMAP with it yet, though.

[bga]

Oh yes, this is definitely implemented. If it is working oor not is another thing. Will look into it this weekend.

[humdinger]

This is implemented, right? I don't use IMAP, so... assigning to Clemens, he knows best.