MM-8180 Improve error message for testing smtp connections (#8608)

* Improve error message for testing smtp connections

* Update error message

app/admin.go

@@ -243,7 +243,7 @@ func (a *App) TestEmail(userId string, cfg *model.Config) *model.AppError {
 		T := utils.GetUserTranslations(user.Locale)
 		license := a.License()
 		if err := utils.SendMailUsingConfig(user.Email, T("api.admin.test_email.subject"), T("api.admin.test_email.body"), cfg, license != nil && *license.Features.Compliance); err != nil {
-			return err
+			return model.NewAppError("testEmail", "app.admin.test_email.failure", map[string]interface{}{"Error": err.Error()}, "", http.StatusInternalServerError)
 		}
 	}
 

i18n/en.json

@@ -7336,12 +7336,16 @@
   },
   {
     "id": "utils.mail.send_mail.from_address.app_error",
-    "translation": "Notification From Address setting is missing or invalid."
+    "translation": "Error setting \"From Address\""
   },
   {
     "id": "utils.mail.send_mail.msg.app_error",
     "translation": "Failed to write email message"
   },
+  {
+    "id": "app.admin.test_email.failure",
+    "translation": "Connection unsuccessful: {{.Error}}"
+  },
   {
     "id": "utils.mail.send_mail.msg_data.app_error",
     "translation": "Failed to add email message data"
@@ -7352,7 +7356,7 @@
   },
   {
     "id": "utils.mail.send_mail.to_address.app_error",
-    "translation": "Notification To Address setting is missing or invalid."
+    "translation": "Error setting \"To Address\""
   },
   {
     "id": "utils.mail.test.configured.error",