If you notice that your emails are not logging to Salesforce via API you will want to check two places.
First, look at how you are configured to log emails to Salesforce here: https://toutapp.com/next#settings/crm/salesforce/configure
Second, check to see if the email failed to log on your Salesforce Activity page in ToutApp: https://toutapp.com/next#settings/crm/salesforce/activity.
Remember that ToutApp will not create a Lead/Contact record for you in Salesforce. If you are not seeing emails log, make sure you have a record in Salesforce with a matching email address.