First of all, you need to find the best email service provider who can carry your bulk emails for you. Some leading ESPs are MailChimp, Constant contact, Drip, Aweber etc. Currently, I am using MailChimp. Quite happy with that. I found the best comparison of ESPs on accuwebhosting blog. You can easily compare all of these providers feature wise.
Apart from that, you must clean your mailing list before sending mass emails. Email Verification is the process of using a specialized software that checks if the email address on your mailing list is safe to send, i.e. Valid or not. Some of the leading email verification service providers that validate email addresses are real or not. They use different techniques to validate catch-all accounts, role, and disposable email addresses etc. Some of the leading email verification service providers are zerobounce, Quickemailverification, Xverify etc.