any extra settings will depend on the smtp servers configuration. it will be different from user to user.
the hurdle for sending mass mailings is to stay within the SMTP serves limits for concurrent connections.
most SMTP servers will have limits set for the number of emails you can send in a given time period.
In the to settings, you can set a time delay for sending each message, and set the maximum number that can be sent in any given time period to stay within the smtp servers limits.