For SMPP/SMS campaigns: Campaign's message content.
It can contains custom variables to be replaced with contact's data, variables have this format : {{varName}}, and value must be replace when requesting a send operation.
For url shortening, it must be specified with a special variable with this format: {{url:the_url}}, for example: {{url:https://indigitall.com}}. The url will be shortened automatically when the campaign is being sent. Url protocol must be included.
If the unsubscription url is wanted in the message, special variable must be placed : {{url:unsubscribe}}