This is more of a generic question, but when should items like this be
METADATA as opposed to a LISTEXT item? To me, POSTADDRESS really feels
like a property of the mailbox as opposed to a property of the
mailstore. I see LISTEXT items as mailstore properties (e.g., one
mailbox is a child of another) and METADATA as mailbox properties. So
I would prefer to see this as a METADATA item.
The main difference is that METADATA data is usually read-write (with
exception of /motd), while POSTADDRESS never is. It has to be generated
by the server.
And both are reported with extended LIST anyway.
Also, METADATA is more difficult to implement on the server. This is not
a problem by itself, but considering my comment above it would require
additional justification. One question worth asking is: does the
POSTADDRESS have to be searchable? I doubt it is.*
*
Plus its MUCH easier to extend using METADATA than LISTEXT - you just
register a new entry - its not a whole new extension, with a new
CAPABILITY etc.
The server still need to know that a value is not writable by the client.
Ideally, the client should recognize the value and don't try to write it.
So in practice both require the same amount of work to be implemented on
the server.
**