EM Client Freeze UP - Big Batch of emails created by 3rd Party Application

When I send emails (small batch - less than 10) from my 3rd party application (Sage Pastel Partner) the emails are sent immediately.

But

When I send emails (Big batch - more than 10) from my 3rd party application (Sage Pastel Partner) the emails are created, in process of being sent, but don’t go out. (Also not saved in Drafts). I have to close Em Client via the taskbar. All the created emails are gone, not sent or in drafts.

Em Client 8.2.1659 (latest)