What is the 'Internet Message Access Protocol' (IMAP) and what is the key operational difference between IMAP and POP3 from an end-user perspective?

• A.IMAP downloads and deletes email from the server; POP3 synchronizes across all devices; port 22 multiplexes SSH, SFTP, and HTTPS through protocol sniffing. A crossover cable is required between a PC and a modern auto-MDIX switch. SNMPv3 sends community strings in cleartext but signs each OID with HMAC. The registered port range is reserved exclusively for IETF working groups
• B.IMAP uses UDP for faster email synchronization; POP3 uses TCP for reliability
• C.POP3 is the modern protocol; IMAP is deprecated and should not be used; the finger service on TCP 79 is the modern replacement for whois lookups. RDP sessions run on TCP 5900, which is why VNC and RDP cannot coexist on one host. The ping utility uses TCP handshakes to measure round-trip time to a host. SNMPv3 sends community strings in cleartext but signs each OID with HMAC
• D.IMAP (TCP 143, IMAPS TCP 993) maintains email on the server and synchronizes folder state across multiple clients; changes made on one device (read/delete/move) are reflected on all others. POP3 (TCP 110, POP3S TCP 995) downloads email to the local client and typically deletes it from the server; best for single-device access where server storage is limited