When you encounter an issue with emails not sending, those emails are not lost, they are (just) stuck in the "queue". Once you have restarted Chilkat, emails in the queue should move out. If it is not always the case, you will need to send them manually.

On VM Desktop PMS, emails are stored on the computer from which they are send. There are four folders managing emails: log, queue, sent and undeliverable. You will find all four of them at this url: C:\ImageTech\VisualMatrix\SmtpQ. The folder to focus is the queue: C:\ImageTech\VisualMatrix\SmtpQ\queue.

Create a separate (temporary) folder on your desktop and transfer all the files from the queue folder to this new one. Then transfer back the files little by little to the queue folder, maybe 5 by 5 and wait for each stack to be send.