I added a new mini project to github: msmtpq_notify .
The following is the content of the README file:
When using msmtpq in front of msmtp all failed connection attempts to the mailserver results in the mail being silently added to the queue.
While this is a desired behaviour in most cases it may be fatal when msmtp or the mail server is misconfigured. In this case msmtp may always fails and mail never becomes delivered.