Alexey presented a new (not yet written) draft on "Externally stored
lists".
The basic idea is to be able to store lists of users or email addresses in
SQL/LDAP/ACAP/...
Such lists can be updated externally, without the need to update Sieve
script.
The proposal is to extend redirect action and header/envelope tests to
reference externally
stored lists.
FYI we support it this kind of way:
if header :is "From" "${Whitelist}" {...}
Where "Whitelist" is an externally configured list of email addresses. Were
I to re-implement, then I'd put "Whitelist" in a namespace. I consider it
along the lines of accessing server configuration, for which we've already
discussed adding a namespace.
The idea of IO bound operations from a sieve script such as LDAP/RBL lookups
makes me twitchy about performance, but these concerns are of course
solvable using multiple threads/processes. I think it's the first time
we've suggested doing this kind of thing, so may be a knock to the
architecture of a few implementations and therefore make it difficult for
them to implement.
Nigel