diff --git a/addons/mail/static/src/model/model_core.js b/addons/mail/static/src/model/model_core.js
index d7de47fcbd7..86e1c8d57a9 100644
--- a/addons/mail/static/src/model/model_core.js
+++ b/addons/mail/static/src/model/model_core.js
@@ -136,7 +136,7 @@ function addOnChanges(modelName, onChanges) {
             if (!Object.prototype.hasOwnProperty.call(onChange, 'methodName')) {
                 throw new Error("at least one onChange definition lacks a methodName (the name of the method to be called on change).");
             }
-            if (!Array.isArray(onChange.dependencies) || onChange.dependencies.some(d => typeof d !== 'string')) {
+            if (!Array.isArray(onChange.dependencies)) {
                 throw new Error("onChange dependencies must be an array of strings.");
             }
             if (typeof onChange.methodName !== 'string') {
@@ -148,6 +148,16 @@ function addOnChanges(modelName, onChanges) {
                     throw new Error(`unknown key "${key}" in onChange definition. Allowed keys: ${allowedKeys.join(", ")}.`);
                 }
             }
+            // paths of dependencies are splitted now to avoid having to do it
+            // each time the path is followed.
+            const splittedDependencies = [];
+            for (const dependency of onChange.dependencies) {
+                if (typeof dependency !== 'string') {
+                    throw new Error("onChange dependencies must be an array of strings.");
+                }
+                splittedDependencies.push(dependency.split('.'));
+            }
+            onChange.dependencies = splittedDependencies;
         }
     }, `Cannot add onChanges to model "${modelName}": `);
     registry.get(modelName).get('onChanges').push(...onChanges);
diff --git a/addons/mail/static/src/model/model_field.js b/addons/mail/static/src/model/model_field.js
index 7aef11a7572..4850ec2f05f 100644
--- a/addons/mail/static/src/model/model_field.js
+++ b/addons/mail/static/src/model/model_field.js
@@ -124,7 +124,15 @@ export class ModelField {
          * the first operation that is able to determine an order for the two
          * records.
          */
-        this.sort = sort;
+        this.sort;
+        /**
+         * Sorted fields define sorting rules that can depend on related fields.
+         * The path to a related field is defined by a period-separated sequence
+         * of the relations to follow. To avoid wasting performances splitting
+         * the path each time a relation must be followed, it is spllited at
+         * field instantiation and stored here.
+         */
+        this.sortedFieldSplittedPaths;
         /**
          * Determines whether and how elements of this field should be summed
          * into a counter field (only makes sense for relational x2many).
@@ -150,16 +158,25 @@ export class ModelField {
                 this.required = true;
             }
         }
-        /**
-         * Automatically make relateds readonly.
-         */
         if (this.related) {
+            // Automatically make relateds readonly.
             this.readonly = true;
         }
         if (this.compute) {
             // Automatically make computes readonly.
             this.readonly = true;
         }
+        if (sort) {
+            this.sort = [];
+            // Only keep unique paths, as they will be used to create listeners,
+            // and we do not want to create useless duplicate listeners.
+            const relatedPathSet = new Set();
+            for (const [compareRule, pathAsString] of sort) {
+                relatedPathSet.add(pathAsString);
+                this.sort.push([compareRule, pathAsString.split('.')]);
+            }
+            this.sortedFieldSplittedPaths = [...relatedPathSet].map(pathAsString => pathAsString.split('.'));
+        }
     }
 
     /**
diff --git a/addons/mail/static/src/model/model_field_relation_set.js b/addons/mail/static/src/model/model_field_relation_set.js
index 3009ab8f072..0e6caf9c699 100644
--- a/addons/mail/static/src/model/model_field_relation_set.js
+++ b/addons/mail/static/src/model/model_field_relation_set.js
@@ -57,8 +57,7 @@ export class RelationSet {
                     // access all useful values of current record (and relations) to mark them as dependencies
                     this.record.modelManager.startListening(listener);
                     const compareDefinition = this.field.sort;
-                    const relatedPathSet = new Set(compareDefinition.map(operation => operation[1])); // only keep unique paths to avoid unnecessary listeners
-                    for (const relatedPath of relatedPathSet) {
+                    for (const relatedPath of this.field.sortedFieldSplittedPaths) {
                         followRelations(value, relatedPath);
                     }
                     this.record.modelManager.stopListening(listener);
diff --git a/addons/mail/static/src/model/model_manager.js b/addons/mail/static/src/model/model_manager.js
index 3b8ccfe841c..f69add7cdd0 100644
--- a/addons/mail/static/src/model/model_manager.js
+++ b/addons/mail/static/src/model/model_manager.js
@@ -526,6 +526,35 @@ export class ModelManager {
         }
     }
 
+    /**
+     * @private
+     * @throws {Error}
+     */
+    _checkOnChangesOnModels() {
+        for (const model of Object.values(this.models)) {
+            for (const { dependencies, methodName } of registry.get(model.name).get('onChanges')) {
+                for (const dependency of dependencies) {
+                    let currentModel = model;
+                    let currentField;
+                    for (const fieldName of dependency) {
+                        if (!currentModel) {
+                            throw new Error(`OnChange '${methodName}' defines a dependency with path '${dependency.join('.')}', but this dependency does not resolve: ${currentField} is not a relational field, therefore there is no relation to follow.`);
+                        }
+                        currentField = currentModel.__fieldMap.get(fieldName);
+                        if (!currentField) {
+                            throw new Error(`OnChange '${methodName}' defines a dependency with path '${dependency.join('.')}', but this path does not resolve: ${currentModel}/${fieldName} does not exist.`);
+                        }
+                        if (currentField.to) {
+                            currentModel = this.models[currentField.to];
+                        } else {
+                            currentModel = undefined;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
     /**
      * @private
      * @throws {Error} in case some fields are not correct.
@@ -580,6 +609,20 @@ export class ModelManager {
                 if (![model.name, 'Record'].includes(inverseField.to)) {
                     throw new Error(`${field} has its inverse ${inverseField} referring to an invalid model (${inverseField.to}).`);
                 }
+                if (field.sort) {
+                    for (const path of field.sortedFieldSplittedPaths) {
+                        let currentField = field;
+                        for (const fieldName of path) {
+                            if (!currentField.to) {
+                                throw new Error(`Field ${field} defines a sort with path '${path.join('.')}', but this path does not resolve: ${currentField} is not a relational field, therefore there is no relation to follow.`);
+                            }
+                            if (!this.models[currentField.to].__fieldMap.has(fieldName)) {
+                                throw new Error(`Field ${field} defines a sort with path '${path.join('.')}', but this path does not resolve: ${this.models[currentField.to]}/${fieldName} does not exist.`);
+                            }
+                            currentField = this.models[currentField.to].__fieldMap.get(fieldName);
+                        }
+                    }
+                }
             }
             for (const identifyingField of model.__identifyingFieldNames) {
                 const field = model.__fieldMap.get(identifyingField);
@@ -921,6 +964,7 @@ export class ModelManager {
          * should have matching reversed relation.
          */
         this._checkProcessedFieldsOnModels();
+        this._checkOnChangesOnModels();
     }
 
     /**
diff --git a/addons/mail/static/src/model/model_utils.js b/addons/mail/static/src/model/model_utils.js
index d7f375d7862..8f075f15299 100644
--- a/addons/mail/static/src/model/model_utils.js
+++ b/addons/mail/static/src/model/model_utils.js
@@ -6,15 +6,12 @@
  * is undefined.
  *
  * @param {Record} record
- * @param {string} relatedPath field names, dot separated to follow relations
+ * @param {string[]} relatedPath Array of field names.
  * @returns {any}
  */
 export function followRelations(record, relatedPath) {
     let target = record;
-    for (const field of relatedPath.split('.')) {
-        if (!target.constructor.__fieldMap.has(field)) {
-            throw Error(`field(${field}) does not exist on ${target}`);
-        }
+    for (const field of relatedPath) {
         target = target[field];
         if (!target) {
             break;