>> 2.  Easy e-mail sync across my devices
>> - laptop/desktop, Android phone/tablet, etc.
>
> IMAP already has that.  It just works.  Not sure why it
> wasn't working for you?
 
Oh, I never said it wasn't working for me.  I never did it because it is folders, not labels, as per the rest of this discussion.  I'm really hooked on labels.
 
> I would also like to see a way for IMAP to handle a post-processor
> adding headers to an email already in the local IMAP data store.
 
Yes!  Something similar and/or related has been in discussions between me and others too.
 
> Heck, I could probably use labels for the same purpose,
> as it amounts to the same thing: adding data/metadata after the fact.
 
Yes, there is some mathematical equivalence here.

 

Say, Trevor, one unrelated peculiarity.  On this reply to your MUUG RoundTable posting, just like on my initial reply last night, my "to" (and "cc") field only had your personal e-mail address, not the MUUG RoundTable address.  This time I caught it before "send" and manually added the MUUG RoundTable address.  Are you doing something unusual in your e-mail, like a jinxed "reply-to"?