Gets the ordinal number of the message in the folder.
A positive integer value representing the ordinal index of the message in the IMAP4 folder.
Unlike Uid values, ordinal message numbers can change due to deleting and expunging messages from the folder.
Note MessageNumber value is guaranteed to be correct even if the envelope could not be parsed (IsValid is true). Thus, the developer can always locate the message whose envelope could not be parsed and which needs to be examined in some other way.
Envelope Class | MailBee.ImapMail Namespace