There are many more than three protocols which can operate at the application layer. Some of these are; Telnet FTP TFTP SMTP IMAP POP DNS RARP BOOTP SNMP CMOT
HTTP Belongs to the Application layer. Other transfer protocols like POP,FTP,SMTP etc also belongs to this layer
Simple Mail Transfer Protocols (SMTP) commands, control and manage the sending of emails by using a set of protocols which are instructions and rules that facilitate the emails transfer across networks.
tftp snmp nfs
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SMTP and POP are two of the three methods for handling email. POP stands for Post Office Protocol and allows you to download email from a server, and SMTP which stands for Simple Mail Transfer Protocol, allows you to send email.
SMTP - 25, 465, and 587 POP - 109, 110, and 995 IMAP - 143, 220, and 993
Gmail uses the technology or the protocols to send mails. It works on port number 487 for SSL. IMAP and SMTP are the protocols used.
SMTP was designed to send email between computers in network. And uses TCP for reliability.
Ftp and smtp ( simple mail transfer protocol)
Both protocols are used to transfer files from one host to another. When transferring the files, both persistent HTTP and SMTP use persistent connections.
SMTP (simple transfer mail protocol) which is used as the outgoing mail server and it uses port number :25 POP3 (Post Office Protocol 3) is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server and it uses port 110