diff --git a/src/user/ServiceManager.ts b/src/user/ServiceManager.ts
index 704ac94..0d983c7 100644
--- a/src/user/ServiceManager.ts
+++ b/src/user/ServiceManager.ts
@@ -274,38 +274,13 @@ class ServiceManager {
         return Promise.resolve()
             .then(function () {
                 const rootDomain = self.dataStore.getRootDomain()
-                const dotRootDomain = `.${rootDomain}`
 
-                if (!customDomain || !/^[a-z0-9\-\.]+$/.test(customDomain)) {
+                try {
+                    Utils.checkCustomDomain(customDomain, appName, rootDomain)
+                } catch (error) {
                     throw ApiStatusCodes.createError(
                         ApiStatusCodes.STATUS_ERROR_BAD_NAME,
-                        'Domain name is not accepted. Please use alphanumerical domains such as myapp.google123.ca'
-                    )
-                }
-
-                if (customDomain.length > 80) {
-                    throw ApiStatusCodes.createError(
-                        ApiStatusCodes.STATUS_ERROR_BAD_NAME,
-                        'Domain name is not accepted. Please use alphanumerical domains less than 80 characters in length.'
-                    )
-                }
-
-                if (customDomain.indexOf('..') >= 0) {
-                    throw ApiStatusCodes.createError(
-                        ApiStatusCodes.STATUS_ERROR_BAD_NAME,
-                        'Domain name is not accepted. You cannot have two consecutive periods ".." inside a domain name. Please use alphanumerical domains such as myapp.google123.ca'
-                    )
-                }
-
-                if (
-                    customDomain.indexOf(dotRootDomain) >= 0 &&
-                    customDomain.indexOf(dotRootDomain) +
-                        dotRootDomain.length ===
-                        customDomain.length
-                ) {
-                    throw ApiStatusCodes.createError(
-                        ApiStatusCodes.STATUS_ERROR_BAD_NAME,
-                        'Domain name is not accepted. Custom domain cannot be subdomain of root domain.'
+                        error
                     )
                 }
             })
diff --git a/src/utils/Utils.ts b/src/utils/Utils.ts
index 381bbd7..7a23735 100644
--- a/src/utils/Utils.ts
+++ b/src/utils/Utils.ts
@@ -120,4 +120,34 @@ export default class Utils {
 
         return Promise.resolve()
     }
+
+    static checkCustomDomain(
+        customDomain: string,
+        appName: string,
+        rootDomain: string
+    ) {
+        const dotRootDomain = `.${rootDomain}`
+        const dotAppDomain = `.${appName}${dotRootDomain}`
+
+        if (!customDomain || !/^[a-z0-9\-\.]+$/.test(customDomain)) {
+            throw 'Domain name is not accepted. Please use alphanumerical domains such as myapp.google123.ca'
+        }
+
+        if (customDomain.length > 80) {
+            throw 'Domain name is not accepted. Please use alphanumerical domains less than 80 characters in length.'
+        }
+
+        if (customDomain.indexOf('..') >= 0) {
+            throw 'Domain name is not accepted. You cannot have two consecutive periods ".." inside a domain name. Please use alphanumerical domains such as myapp.google123.ca'
+        }
+
+        if (
+            customDomain.indexOf(dotAppDomain) === -1 &&
+            customDomain.indexOf(dotRootDomain) >= 0 &&
+            customDomain.indexOf(dotRootDomain) + dotRootDomain.length ===
+                customDomain.length
+        ) {
+            throw 'Domain name is not accepted. Custom domain cannot be subdomain of root domain.'
+        }
+    }
 }
diff --git a/tests/utils.test.ts b/tests/utils.test.ts
index 505dcb6..6b0777b 100644
--- a/tests/utils.test.ts
+++ b/tests/utils.test.ts
@@ -83,3 +83,44 @@ test('Testing filter in place - remove 2nd', () => {
     expect(originalArray[0].val1).toBe('e-1-1')
     expect(originalArray[0].val2).toBe('e-2-1')
 })
+
+test('Testing code to check custom domain', () => {
+    const rootDomain = 'google123.ca'
+    const appName = 'app1'
+
+    expect(() => Utils.checkCustomDomain('', appName, rootDomain)).toThrow(
+        'Domain name is not accepted. Please use alphanumerical domains such as myapp.google123.ca'
+    )
+
+    expect(() =>
+        Utils.checkCustomDomain('x'.repeat(81), appName, rootDomain)
+    ).toThrow(
+        'Domain name is not accepted. Please use alphanumerical domains less than 80 characters in length.'
+    )
+
+    expect(() =>
+        Utils.checkCustomDomain('..google321.ca', appName, rootDomain)
+    ).toThrow(
+        'Domain name is not accepted. You cannot have two consecutive periods ".." inside a domain name. Please use alphanumerical domains such as myapp.google123.ca'
+    )
+
+    expect(() =>
+        Utils.checkCustomDomain(`app2.${rootDomain}`, appName, rootDomain)
+    ).toThrow(
+        'Domain name is not accepted. Custom domain cannot be subdomain of root domain.'
+    )
+
+    expect(() =>
+        Utils.checkCustomDomain(
+            `api.${appName}.${rootDomain}`,
+            appName,
+            rootDomain
+        )
+    ).not.toThrow(
+        'Domain name is not accepted. Custom domain cannot be subdomain of root domain.'
+    )
+
+    expect(() =>
+        Utils.checkCustomDomain(`caprover123.ca`, appName, rootDomain)
+    ).not.toThrow()
+})