I have been dealing with emailing issue from one of my clients websites for a while now. One SMTP provider had issues and bad service. Pepipost is one I will never use again. I switched to another SMTP provide and that service seemed to have issues. The biggest issues I ran into is that these providers wanted my client to use their site for report bounces, opens, and deliveries. However, we want to use the reporting that is part of the CRM. That platform also auto holds email after a number of rejections, allows the users the unsubscribe and other required functions.
The final answer was to change our CRM to send email through the web-host. After making all the changes, including outgoing email accounts, bounce accounts, etc we were all set. Now we are able to see reports of how effective our email list are doing.
Special thanks to the support staff at backyllchosting.com