This function only marks the message for deletion. The message
is not actually deleted until the mailbox is expunged or another
mailbox is selected. This function will return an error if the
current mailbox is in read-only mode, such as if it was selected
using the ExamineMailbox method.
It is important to note that unlike the POP3 protocol, a message
that is marked for deletion is still accessible on the IMAP server
until the mailbox is expunged. This means, for example, that a
deleted message can still be retrieved using the GetMessage
method.
To determine if a message has been marked for deletion, set the
Message property to the message number and then check the
value of the MessageFlags property to determine if the
imapFlagDeleted bit flag has been set.
To remove the deletion flag from the message, use the
UndeleteMessage method. To prevent all messages in the
current mailbox from being expunged, use the ReselectMailbox
function to reset the current mailbox state. Calling the
Reset method will also unselect the current mailbox without
expunging deleted messages.