The customer use DocHouse 4. This third-party system accesses the mail files on Cloud but will work more efficient and reliable if there was an presorting on server already done.
Internet Message Access Protocol - SORT and THREAD Extensions
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
This document describes the base-level server-based sorting and
threading extensions to the IMAP protocol. These extensions provide
substantial performance improvements for IMAP clients that offer
sorted and threaded views.
The SORT and THREAD extensions to the [IMAP] protocol provide a means
of server-based sorting and threading of messages, without requiring
that the client download the necessary data to do so itself. This is
particularly useful for online clients as described in [IMAP-MODELS].
A server that supports the base-level SORT extension indicates this
with a capability name which starts with "SORT". Future, upwards-
compatible extensions to the SORT extension will all start with
"SORT", indicating support for this base level.
A server that supports the THREAD extension indicates this with one
or more capability names consisting of "THREAD=" followed by a
supported threading algorithm name as described in this document.
This provides for future upwards-compatible extensions.
A server that implements the SORT and/or THREAD extensions MUST
collate strings in accordance with the requirements of I18NLEVEL=1,
as described in [IMAP-I18N], and SHOULD implement and advertise the
I18NLEVEL=1 extension. Alternatively, a server MAY implement
I18NLEVEL=2 (or higher) and comply with the rules of that level.