User IDs are integers. When you send a message, it will be sent to receivers 0 through <number of recipients - 1>.
Currently, number of receivers is limited to 2000.
From: brett
Body: okay body
Number of recipients: 2000
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRiGCAw
From: brett
Body: okay body
Number of recipients: 2000
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRiHCAw
From: brett
Body: okay body
Number of recipients: 2000
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRiICAw
From: w
Body: hello
Number of recipients: 2000
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRiJCAw
From: lkjlkj
Body: jlkdjf lkjgsdfg
Number of recipients: 234
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRiPLww
From: lkjlkj
Body: jlkdjf lkjgsdfg
Number of recipients: 234
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRiSLww
From: sgfdfg
Body: hi
Number of recipients: 900
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRjuNgw
From: Franki
Body: Hi there
Number of recipients: 230
Key: agtwdWJzdWItdGVzdHIOCxIHTWVzc2FnZRiVfQw
From: blah
Body: GOGO
Number of recipients: 200
Key: agtwdWJzdWItdGVzdHIPCxIHTWVzc2FnZRiChQEM
From: blah
Body: GOGO
Number of recipients: 200
Key: agtwdWJzdWItdGVzdHIPCxIHTWVzc2FnZRiEhQEM