Sending emails with delay as well as to only few email addresses

Recently I have issue phpList does not send email to all participants. I see large number of bounced email addresses but I know these email addresses are correct but some how phpList only sending to 10% of total email addresses we have 2016 email addresses in distribution.

You need to look at some of the bounces to see the underlying reason. It might be something else, such as sending too quickly.