SMTP, IMAP, and POP3 are TCP protocols that set the standards to send and receive emails. SMTP sends emails, while the other two protocols collect them. Webmail and email clients are two types of email providers. Webmail is an email app that’s accessed through a browser like Gmail or Hotmail. Microsoft Outlook, Windows Live, and Mozilla Thunderbird are email software and would be considered email clients. You install email clients on a computer or other personal device like your phone or tablet
SMTP (Simple Mail Transfer Protocol) is the protocol for sending out emails from both email clients and webmail. Sometimes, the person sending as well as the person receiving the email have opposite providers (meaning from an email client like Microsoft Outlook to Gmail. SMTP is also used to forward email messages.
POP (Post Office Protocol) was originally made to store emails offline for viewing anytime as well as storage purposes. The first version of POP was in 1984, with POP2 made in 1985. POP3 is the latest version, first introduced in 1988, that supports extensions and authentication options. POP3 is used to collect email messages from a mail server that then go to a mail client. POP3 also deletes copies of the messages stored on the server, and then disconnects. Once the emails are gone, the user cannot log on from elsewhere and see those same emails, they can only be viewed in the email client on their personal device because that is where they were downloaded to and saved.
IMAP (Internet Messaging Access Protocol) is the protocol that was created in 1986, and keeps all emails stored on the server. The idea behind IMAP was keep users from having to be restricted to one email client, giving them the ability to read their emails from anywhere. The user can access all their emails from more than one device at the same time too. One drawback of IMAP storing messages on the server would be that it takes up space.