CIPP/US Study Guide
Chapter 3: Introduction to Technological Aspects of Privacy

How Emails and Texts Work: SMTP, IMAP, POP, SMS and OTT

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SMTP sends email; IMAP (which leaves mail on the server) is overtaking POP (which deletes it). Texts use SMS (160-character limit, works without internet) or internet-based over-the-top (OTT) services that can offer end-to-end encryption. CAN-SPAM and the TCPA govern marketing messages.

Email receiving protocols
ProtocolBehavior
IMAPTypically leaves messages on the server; enables synchronization across multiple devices and server-side search; increasingly common
POPTypically deletes mail from the server; used less over time

For sending, SMTP is most common. Texts began with SMS (160-character limit, can run on cell service without internet) and have shifted to over-the-top (OTT) services like iMessage, Signal, Telegram, and WhatsApp, which lack SMS limits and can provide end-to-end encryption.

Marketing message laws

CAN-SPAM (Chapter 11) requires commercial email marketing to honor opt-outs, and the Telephone Consumer Protection Act (TCPA) (Chapter 11) regulates marketing via text messages. Know which applies to email vs text.

Key terms - quick answers

What is “SMTP”?
Simple Mail Transfer Protocol, the most common protocol for sending email.
What is “IMAP”?
Internet Message Access Protocol for receiving email; typically leaves messages on the server, enabling multi-device sync and server-side search.
What is “POP”?
Post Office Protocol (POP3) for receiving email; typically deletes mail from the server and is used less over time.
What is “SMS”?
Short Message Service using the Short Message Peer to Peer Protocol; limited to 160 characters and able to operate over cell service without the internet.

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