Email Archive and Announcement contain ascending and descending versions of the same index. However, according to mysql http://dev.mysql.com/doc/refman/5.5/en/create-index.html
An index_col_name specification can end with ASC or DESC. These keywords are permitted for future extensions for specifying ascending or descending index value storage. Currently, they are parsed but ignored; index values are always stored in ascending order.
The DESC indexes are therefore duplicates that serve no purpose in mysql and should be removed.
CREATE INDEX IE_MAILARC_MSG_DATE ON MAILARCHIVE_MESSAGE
CREATE INDEX IE_MAILARC_MSG_DATE_DESC ON MAILARCHIVE_MESSAGE