I have a messaging software used for sending out messages in bulk and individually, the issue now is that when I select the contacts (lets say over 100,000 contacts) that I want to send this message to and send it stays there and continue loading and after a while the server times out and not all the contacts receives the message (meaning some received the message).

I need to understand the sequence with which the messages are the go out, if I am to batch the messages or the best course of action to take.