Your answer to a question about a protocol should begin with the definition of the protocol, followed by a brief description of its use. Providing examples of how you used this in your previous roles will verify your qualifications and make it more likely you will be offered the job. It is best to use examples that align with the business operations and technologies of the organization with whom you are interviewing.

"SMTP stands for simple mail transfer protocol. It defines the standards used when sending and receiving emails across the internet. Email application developers adhere to this protocol to ensure that their programs can exchange email with similar applications using various platforms and operating systems. Functions such as end-to-end and in store-and-forward are supported within SMTP."