Writer Serienbrief Parameter Pause zwischen E-Mails

Hello,
How is it possible to define the pause between the E-Mails sent (seconds). This is required to avoid a throttling by the mail server if too many E-Mails are sent in a certain period (e.g. 300 / hr).
Thank you!

I asked this question already on Sept 25 2017, how long does it normally take until a question appears in this ALO?
Edited: Seems to appear immediatelly after clicking on ‘Frage stellen’ below “I’m not a robot” (which answers next question as well).

What is ‘Frage stellen’ below “I’m not a robot” for? Is it to send this question or to ask a new one?
Edited: Seems to funcition as ‘Send the question’