Safely Sending out hundreds of e-mails?

Hi,

I started making a plugin that sends e-mails to users via the wp_mail function. I also installed another plugin (WP SMTP) that allows me to connect to an SMTP server. Different content is sent to each user, and it should work to send to hundreds of users.

Right now, it loops through all of users and sends the mail to each of them with their specific content. It seems to send about the first 80-100 emails then it stops.

I need to ensure that the e-mails go through to hundreds of users when I send. I realize this is probably a very inefficient way to do it, since i’m using shared servers. How can I ensure that the mails go through?