I have been trying to implement Mailpoet3 + Siteground for some three months now.
Initially all seemed well – but the CPU overrun issue has recurred.
I have updated to the latest release and switched from using the user driven option on Siteground to mailing via Gmail.
Yet again the site has been taken down due to CPU overrun!
Clearly the latest plugin release does not fix the problem.
Mailpoet offers significant advantages due to its integration with WP.
However, unless this problem is resolved quickly, I will have to resort to an alternative solution.