The Delete method removes all the Message objects from the Messages collection.
collMessages.Delete( )
The Delete method performs an irreversible operation on the collection. It calls Release on the collection's reference to every Message object. If you have another reference to a message, you can still access its properties and methods, but you can never again associate it with any collection because the Add method always creates a new object. You should Set your reference variable either to Nothing or to another item.
The final Release on each Message object takes place when you call Delete if you had no other reference, or when you assign your reference variable to Nothing. At this point the object is removed from memory. Attempted access to a released object results in an error return of CdoE_INVALID_OBJECT.
Be cautious using the Delete method with a collection, because it deletes all the collection's member objects. To delete only one Message object, use the Delete method specific to that object.
The Delete method on a large collection takes effect immediately and is permanent. A deleted member cannot be recovered. However, the collection itself is still valid, and you can Add new members to it.