diff --git a/ontology/observable/observable.ttl b/ontology/observable/observable.ttl
index a34698b8..73fec9e8 100644
--- a/ontology/observable/observable.ttl
+++ b/ontology/observable/observable.ttl
@@ -3525,6 +3525,12 @@ observable:MessageFacet
 			sh:maxCount "1"^^xsd:integer ;
 			sh:nodeKind sh:Literal ;
 			sh:path observable:sessionID ;
+		] ,
+		[
+			sh:datatype vocabulary:MessageDeliveryStateVocab ;
+			sh:maxCount "1"^^xsd:integer ;
+			sh:nodeKind sh:Literal ;
+			sh:path observable:messageDeliveryState ;
 		]
 		;
 	sh:targetClass observable:MessageFacet ;
@@ -10165,6 +10171,13 @@ observable:message
 	rdfs:range observable:ObservableObject ;
 	.
 
+observable:messageDeliveryState
+	a owl:DatatypeProperty ;
+	rdfs:label "messageDeliveryState"@en ;
+	rdfs:comment "The delivery state (i.e. received, delivered, sent, etc.) of an incoming or outgoingmessage (i.e. text message, email, etc.)."@en ;
+	rdfs:range vocabulary:MessageDeliveryStateVocab ;
+	.
+
 observable:messageID
 	a owl:DatatypeProperty ;
 	rdfs:label "messageID"@en ;
diff --git a/ontology/vocabulary/vocabulary.ttl b/ontology/vocabulary/vocabulary.ttl
index 83f6e472..7d8e4857 100644
--- a/ontology/vocabulary/vocabulary.ttl
+++ b/ontology/vocabulary/vocabulary.ttl
@@ -601,6 +601,29 @@ vocabulary:MemoryBlockTypeVocab
 	) ;
 	.
 
+vocabulary:MessageDeliveryStateVocab
+	a rdfs:Datatype ;
+	rdfs:subClassOf rdfs:Resource ;
+	rdfs:label "Message Delivery State Vocabulary"@en-US ;
+	owl:oneOf (
+		"Archived"^^vocabulary:MessageDeliveryStateVocab
+		"Deleted"^^vocabulary:MessageDeliveryStateVocab
+		"Delivered"^^vocabulary:MessageDeliveryStateVocab
+		"Delivered_Read"^^vocabulary:MessageDeliveryStateVocab
+		"Delivered_Unread"^^vocabulary:MessageDeliveryStateVocab
+		"Forwarded"^^vocabulary:MessageDeliveryStateVocab
+		"Forwarding"^^vocabulary:MessageDeliveryStateVocab
+		"Read"^^vocabulary:MessageDeliveryStateVocab
+		"Replied"^^vocabulary:MessageDeliveryStateVocab
+		"Replying"^^vocabulary:MessageDeliveryStateVocab
+		"Sending_Failed"^^vocabulary:MessageDeliveryStateVocab
+		"Sent"^^vocabulary:MessageDeliveryStateVocab
+		"Unpublished"^^vocabulary:MessageDeliveryStateVocab
+		"Unread"^^vocabulary:MessageDeliveryStateVocab
+		"Unsent"^^vocabulary:MessageDeliveryStateVocab
+	) ;
+	.
+
 vocabulary:ObservableObjectRelationshipVocab
 	a rdfs:Datatype ;
 	rdfs:subClassOf rdfs:Resource ;