Support for special date (661) column to represent the date of a mail message. As configured, either the internal received date or mail's sent date (as given by Date header).

Supposed to be the replacement for sent_date (609) or received_date (610) to let the Open-Xchange Middleware decide based on configuration for com.openexchange.mail.preferSentDate property what to consider. Supported at both - columns parameter and sort parameter.