Add time delay between emails when New Product/Newsletter emails are sent

Hosting: Siteground
Zen Cart 155F
Winchester Responsive

When I attempt to send emails to everyone that signed up for our New Product announcements & Newsletter we get errors.

Maybe 10 emails send fine (Turn Green in Header) Then the rest are red I forget the reason it says they did not send.

I then take down the names of the ones that show Green and resend the ones that did not go through and repeat this until they are completed.

Our Hosting Company for the website says that it is because of the speed the emails are being sent.

Question:

Is there anyway to adjust the speed that the Newsletter/New Products emails are being sent from within Zen Cart (menus or code adjustments)?

Is there a better way to do this task than from within Zen Cart?

I just looked through the Log files and found this event. Maybe it will assist someone with an answer. I have edited it to hide any personal emails and such!

Email Error: SMTP Error: The following recipients failed: Someones email address: *****.siteground.biz received more than 10.1 messages for 1s . Service
temporary unavailable, message deffered, try again later.

Seems like in any such loop to send email that prior to the loop starting would want to capture the time, then in the loop would want a timer loop to occur such that the email is not sent or the email loop is not started until a particular period of time has passed.

The easier way to do this is to use a service designed to perform and handle this type of action like mailchimp or some other.