Holds next free unique ID for the messages.

A Long value.  

object.NextMessageUID [= value]

The NextMessageUID Property syntax has these parts:

Just as each folder must have his own UID (unique ID), each message must also have unique ID within same folder - and each new message that is created must get its own UID which is never smaller than any previous message within same folder. This is very important for client's behavior - if you violate this specification then client may get confused - thinking that some message is too old and he might not be interested in it.

NextMessageUID property will hold first available UID to be given to new message. This is default value that wodImapServer assigns each time you call Messages.Add method. Of course - you can always override given UID and assign one you want.

Each time wodImapServer assigns new UID to new message, it will internally increase this value by one. You can always put new long integer value to this property to let wodImapServer know how to assign new UIDs to newly created messages.