Gets UID (Unique-ID) assigned to the message in the folder on the mail server.
MailBee.NET (in MailBee.NET.dll) Version: 12.2.0 build 630 for .NET 4.5
Public ReadOnly Property Uid As Long
A positive 32-bit numeric value indicating UID of the message, or -1 if this information is not available.
Unlike ordinal message numbers (MessageNumber
property), UIDs persist
between operations which re-order messages in a folder (such as deleting and expunging messages).
Also, UIDs should persist between different IMAP sessions (some old IMAP4 implementations, however, may violate
this rule, see UidValidity
topic for details).