How send bulk email or newsletter?

It really depends on the features you want. I think mailgun are the the best per value for basic features.

They have an official PHP SDK too:
https://github.com/mailgun/mailgun-php

Thanks this worked for me.

The most popular method for sending emails to numerous recipients at the same time is the BCC (Blind Carbon Copy) method.

When you use the BCC option to email many people, it hides the other receivers from the receiver, making it appear as though he is the only one who received the email.

To use the BCC approach, follow these five steps:-

Log into your Gmail account.
Select the Compose box.
Select BCC from the drop-down menu.
Complete the BCC field.
Send the message.