Returns the number of messages waiting from the most recent
public void SetSummarizeOnBind(boolean val)
When binding to the Message Store, by default it checks the number of
messages that are available to be read (regardless of their status).
This operation can be quite expensive if there are lots of messages in
the mailbox. If you want to speed up the bind operation, then
The default is SetSummarizeOnBind(true).
If you want to find out how many messages are available, use GetNumMsgs()