CentralNotice Simple Mail Transfer Protocol From Wikipedia, the free encyclopedia Jump to: navigation , search "SMTP" redirects here. For the email delivery company, see SMTP (company) . Internet protocol suite Application layer BGP DHCP AAA/AAAS DNS FTP HTTP IMAP LDAP MGCP NNTP NTP POP ONC/RPC RADIUS RTP RTSP RIP SIP SMTP SNMP SSH TACACS Telnet TLS/SSL XMPP more... Transport layer TCP UDP DCCP SCTP RSVP more... Internet layer IP IPv4 IPv6 ICMP ICMPv6 ECN IGMP IPsec more... Link layer ARP NDP OSPF Tunnels L2TP PPP MAC Ethernet DSL ISDN FDDI more... v t e Internet An Opte Project visualization of routing paths through a portion of the Internet. General Access Censorship Democracy Digital divide Digital rights Freedom of information History of the Internet Internet phenomena Net neutrality Pioneers Privacy Soc...