Final answer:
The network technician is following the Bottom-up approach for troubleshooting the e-mail issue by starting with the physical cable connections.
Step-by-step explanation:
The troubleshooting approach being followed when a network technician first verifies the physical connectivity of cables when a user is unable to send an e-mail is known as the Bottom-up approach. This methodology begins by checking the most fundamental elements such as cables, hardware devices, and gradually advances towards software, configuration, and application issues. This contrasts with the Top-down approach, which starts with software and user-facing applications and works its way down to the physical components. The Divide and conquer and Step-by-step approaches are different strategies that could also be used in troubleshooting complex problems.