This video shows how to send one-off email/SMS broadcasts such as monthly newsletters:
There are 3 Steps to the process:
1. Build the campaign you would like to send (for example an email and a single SMS)
2. Decided which contacts you would like to send it to.
3. Execute a 'Bulk Request' to deliver your campaign to your contacts.
By setting that campaign to 'allow multiple' you can re-use the same campaign the following week simply by adjusting the email and other messages and running another bulk request.