Discuss email and messaging protocols, using examples that you have explored using wireshark.
Can we send email with just telnet (or ncat or similar tool) ... if we can find the right gateway.
Note that phones are not a TCP/IP network ... nor is SMS (short message service), though there are some gateways ... such as when your iphone tries to use a wifi connection for a phone call. These services are typicall company-based (apple, google) using proprietary systems.
How does all this encryption stuff work anyway?
Things to understand
And then there's the (much) larger internet security topic ...
End of term project(s) ...
Gmail making email more secure with MTA-STS standard (yesterday ...) | hackernews discussion