Which of the following is a way to establish contact with a digital messaging system gateway station?

To connect to a digital messaging system gateway, such as a Winlink RMS node or a packet radio BBS, you must actively initiate the communication on the RF frequency where the gateway station is listening. The correct procedure is to configure your client software with the gateway's callsign and transmit a specific 'connect message' on the station's published frequency. Once the gateway hears your request, it will respond and establish the digital handshake. The other options do not apply to this process. Sending an email defeats the purpose of making an RF connection, 'QRL' is a Morse code prosign used to ask if a frequency is busy, and passively waiting for an SSID broadcast is a Wi-Fi concept, not how amateur digital gateways operate.