The Size property sets filtering on a message's approximate total size in bytes. Read/write.
objMessageFilter.Size
Long
The Size property specifies that the message filter should pass only messages with approximate total size greater than the value of Size.
The Size property represents the sum of all the message's MAPI properties, including the Subject, Text, Attachments, and Recipients.
The Size property corresponds to the MAPI property PR_MESSAGE_SIZE.