diff --git a/src/v0/destinations/mp/data/MPIdentifyConfig.json b/src/v0/destinations/mp/data/MPIdentifyConfig.json
index 44c99fb56d..0abe7826f0 100644
--- a/src/v0/destinations/mp/data/MPIdentifyConfig.json
+++ b/src/v0/destinations/mp/data/MPIdentifyConfig.json
@@ -1,15 +1,13 @@
 [
   {
     "destKey": "$created",
-    "sourceKeys": "createdAtOnly",
-    "required": false,
-    "sourceFromGenericMap": true
+    "sourceKeys": ["createdAt","traits.createdAt", "context.traits.createdAt"],
+    "required": false
   },
   {
     "destKey": "$email",
-    "sourceKeys": "email",
-    "required": false,
-    "sourceFromGenericMap": true
+    "sourceKeys": ["email","traits.email", "context.traits.email", "properties.email", "context.externalId.0.id"],
+    "required": false
   },
   {
     "destKey": "$first_name",
@@ -24,24 +22,33 @@
       "context.traits.firstname",
       "context.traits.first_name"
     ],
-    "required": false,
-    "sourceFromGenericMap": true
+    "required": false
   },
   {
     "destKey": "$last_name",
-    "sourceKeys": "lastName",
-    "required": false,
-    "sourceFromGenericMap": true
+    "sourceKeys": [
+      "lastName",
+      "lastname",
+      "last_name",
+      "traits.lastName",
+      "traits.lastname",
+      "traits.last_name",
+      "context.traits.lastName",
+      "context.traits.lastname",
+      "context.traits.last_name"
+    ],
+    "required": false
   },
   {
     "destKey": "$name",
-    "sourceKeys": "name",
-    "required": false,
-    "sourceFromGenericMap": true
+    "sourceKeys": ["name","traits.name", "context.traits.name"],
+    "required": false
   },
   {
     "destKey": "$username",
     "sourceKeys": [
+      "username",
+      "userName",
       "traits.username",
       "context.traits.username",
       "traits.userName",
@@ -51,18 +58,19 @@
   },
   {
     "destKey": "$phone",
-    "sourceKeys": "phone",
-    "required": false,
-    "sourceFromGenericMap": true
+    "sourceKeys": ["phone","traits.phone", "context.traits.phone"],
+    "required": false
   },
   {
     "destKey": "$avatar",
-    "sourceKeys": ["traits.avatar", "context.traits.avatar"],
+    "sourceKeys": ["avatar","traits.avatar", "context.traits.avatar"],
     "required": false
   },
   {
     "destKey": "$country_code",
     "sourceKeys": [
+      "country",
+      "address.country",
       "traits.address.country",
       "context.traits.address.country",
       "traits.country",
@@ -74,6 +82,8 @@
   {
     "destKey": "$city",
     "sourceKeys": [
+      "city",
+      "address.city",
       "traits.city",
       "context.traits.city",
       "traits.address.city",
@@ -85,6 +95,9 @@
   {
     "destKey": "$region",
     "sourceKeys": [
+      "state",
+      "address.state",
+      "location.region",
       "traits.state",
       "context.traits.state",
       "traits.address.state",
@@ -95,7 +108,7 @@
   },
   {
     "destKey": "$geo_source",
-    "sourceKeys": "context.location.geoSource",
+    "sourceKeys": ["location.geoSource","context.location.geoSource"],
     "required": false
   },
   {
@@ -145,7 +158,7 @@
   },
   {
     "destKey": "$unsubscribed",
-    "sourceKeys": ["traits.unsubscribed", "context.traits.unsubscribed", "properties.unsubscribed"],
+    "sourceKeys": ["unsubscribed","traits.unsubscribed", "context.traits.unsubscribed", "properties.unsubscribed"],
     "required": false
   },
   {
diff --git a/src/v0/destinations/mp/transform.js b/src/v0/destinations/mp/transform.js
index 9cf43b88f7..69f5d2bc7f 100644
--- a/src/v0/destinations/mp/transform.js
+++ b/src/v0/destinations/mp/transform.js
@@ -17,6 +17,7 @@ const {
   checkInvalidRtTfEvents,
   handleRtTfSingleEventError,
   groupEventsByType,
+  extractCustomFields,
 } = require('../../util');
 const {
   ConfigCategory,
@@ -27,6 +28,7 @@ const {
   TRACK_MAX_BATCH_SIZE,
   ENGAGE_MAX_BATCH_SIZE,
   GROUPS_MAX_BATCH_SIZE,
+  MP_IDENTIFY_EXCLUSION_LIST,
 } = require('./config');
 const {
   createIdentifyResponse,
@@ -241,28 +243,37 @@ function trimTraits(traits, contextTraits, setOnceProperties) {
   const contextTraitsCopy = { ...contextTraits };
 
   // Initialize setOnce object
-  const setOnce = {};
+  const setOnceEligible = {};
 
-  // Iterate over setOnceProperties and move corresponding properties to setOnce
-  setOnceProperties.forEach((property) => {
-    if (traitsCopy.hasOwnProperty(property)) {
-      setOnce[property] = traitsCopy[property];
-      delete traitsCopy[property];
+  // Step 1: find the k-v pairs of setOnceProperties in traits and contextTraits
+
+  setOnceProperties.forEach((propertyPath) => {
+    const pathSegments = propertyPath.split('.');
+    const propName = pathSegments[pathSegments.length - 1];
+
+    if (Object.keys(traitsCopy).length > 0 && get(traitsCopy, propertyPath)) {
+      setOnceEligible[propName] = get(traitsCopy, propertyPath);
+      lodash.unset(traitsCopy, propertyPath);
     }
-    if (contextTraitsCopy.hasOwnProperty(property)) {
-      if(!setOnce.hasOwnProperty(property)) {
-        setOnce[property] = contextTraitsCopy[property];
+    if (Object.keys(contextTraits).length > 0 && get(contextTraitsCopy, propertyPath)) {
+      if(!setOnceEligible.hasOwnProperty(propName)) {
+        setOnceEligible[propName] = get(contextTraitsCopy, propertyPath);
       }
-      delete contextTraitsCopy[property];
+      lodash.unset(contextTraitsCopy, propertyPath);
     }
   });
+  // Step 2: transform properties eligible as per rudderstack declared identify event mapping
+  // setOnce should have all traits from message.traits and message.context.traits by now
+  let sentOnceTransform = constructPayload(setOnceEligible, mPIdentifyConfigJson);
+
+  // Step 3: combine the transformed and custom setOnce traits
 
-  const sentOnceTransform = constructPayload(setOnce, mPIdentifyConfigJson);
+  sentOnceTransform = extractCustomFields(setOnceEligible, sentOnceTransform, 'root', MP_IDENTIFY_EXCLUSION_LIST);
 
   return {
     traits: traitsCopy,
     contextTraits: contextTraitsCopy,
-    sentOnceTransform,
+    setOnce: sentOnceTransform,
   };
 }
 
diff --git a/test/integrations/destinations/mp/common.ts b/test/integrations/destinations/mp/common.ts
index e2daaa8622..f5efc4cc48 100644
--- a/test/integrations/destinations/mp/common.ts
+++ b/test/integrations/destinations/mp/common.ts
@@ -38,6 +38,12 @@ const destinationWithSetOnceProperty = {
     setOnceProperties: [
       {
         property: 'nationality'
+      },
+      {
+        property: 'firstName'
+      },
+      {
+        property: 'address.city'
       }
     ],
     superProperties: [
diff --git a/test/integrations/destinations/mp/processor/data.ts b/test/integrations/destinations/mp/processor/data.ts
index 7038a24fac..e5313a93fe 100644
--- a/test/integrations/destinations/mp/processor/data.ts
+++ b/test/integrations/destinations/mp/processor/data.ts
@@ -5992,7 +5992,7 @@ export const data = [
       request: {
         body: [
           {
-            description: 'Alias: with property beyond exclusion list',
+            description: 'Alias: with property beyond and within exclusion list',
             destination: destinationWithSetOnceProperty,
             message: {
               anonymousId: 'e6ab2c5e-2cda-44a9-a962-e2f67df78bca',
@@ -6018,7 +6018,9 @@ export const data = [
                   density: 2
                 },
                 traits: {
-                  city: 'Disney',
+                  address: {
+                    city: 'Disney',
+                  },
                   country: 'USA',
                   email: 'TestSanity@disney.com',
                   firstName: 'Mickey test',
@@ -6072,7 +6074,7 @@ export const data = [
                 FORM: {},
                 JSON: {},
                 JSON_ARRAY: {
-                  batch: "[{\"$set_once\":{\"nationality\":\"USA\"},\"$token\":\"dummyToken\",\"$distinct_id\":\"Santiy\"}]",
+                  batch: "[{\"$set_once\":{\"$first_name\":\"Mickey test\",\"$city\":\"Disney\",\"nationality\":\"USA\"},\"$token\":\"dummyToken\",\"$distinct_id\":\"Santiy\"}]",
                 },
                 XML: {},
               },
@@ -6093,7 +6095,7 @@ export const data = [
                 FORM: {},
                 JSON: {},
                 JSON_ARRAY: {
-                  batch: "[{\"$set\":{\"$created\":\"2020-01-23T08:54:02.362Z\",\"$email\":\"TestSanity@disney.com\",\"$country_code\":\"USA\",\"$city\":\"Disney\",\"$initial_referrer\":\"https://docs.rudderstack.com\",\"$initial_referring_domain\":\"docs.rudderstack.com\",\"$name\":\"Mickey test VarChange\",\"random\":\"superProp\",\"$firstName\":\"Mickey test\",\"$lastName\":\"VarChange\",\"$browser\":\"Chrome\",\"$browser_version\":\"79.0.3945.117\"},\"$token\":\"dummyToken\",\"$distinct_id\":\"Santiy\",\"$ip\":\"0.0.0.0\",\"$time\":null}]",
+                  "batch": "[{\"$set\":{\"$created\":\"2020-01-23T08:54:02.362Z\",\"$email\":\"TestSanity@disney.com\",\"$country_code\":\"USA\",\"$initial_referrer\":\"https://docs.rudderstack.com\",\"$initial_referring_domain\":\"docs.rudderstack.com\",\"random\":\"superProp\",\"$lastName\":\"VarChange\",\"$browser\":\"Chrome\",\"$browser_version\":\"79.0.3945.117\"},\"$token\":\"dummyToken\",\"$distinct_id\":\"Santiy\",\"$ip\":\"0.0.0.0\",\"$time\":null}]"
                 },
                 XML: {},
               },