Internet Direct (Indy) Version 9.0.1 Beta
TIdMailBox.UIDValidity
Indicates the mailbox UID value for a messaged added to the mailbox.

property UIDValidity: String;
Description
UIDValidity is a String property that indicates the Unique Identifier Validity value for the currently selected mailbox. UIDValidity is used with UIDNext to determine the permanent Uniqueness identifier for a message in the currently selected mailbox.

UIDValidity is updatd when the IMAP4 client executes the TIdIMAP4.StatusMailBox method, or when a new mailbox is selected using TIdIMAP4.SelectMailBox.