What is the difference between SMTP, POP3 and IMAP?

There are three standards currently used by most electronic mail (email) services. These are SMTP, POP3 and IMAP. The standard SMTP are the acronyms for Simple Mail Transfer Protocol (Simple Mail Transfer Protocol). POP is the acronym for Post Office Protocol (Post Office Protocol). Although it may sound a bit confusing, POP is the email storage protocol while SMTP is the sending and receiving protocol. POP3 it is the third developed version of the POP standard. IMAP (Internet Message Access Protocol) is another more modern storage protocol than POP3 and with more possibilities.

If we make an analogy with postal mail, the SMTP protocol would be analogous to the postman or letter transport services. He or she delivers and collects mail for transfer to another location. The POP3 protocol and the IMAP protocol would be like your mailbox at home or a post office box. It is the place where the mail is sent and where it remains until the recipient is ready to read it. Outgoing mail can also be put in the mailbox, ie POP3 and IMAP protocols are also used to store sent mail.

SMTP: the transport of emails

The vast majority of emails that travel over the Internet do so using the SMTP standard, a transfer protocol. Although it was invented in the early 1980s, it is considered a very reliable protocol, which is the main reason why it remains the most widely used almost universally. Most emails sent using SMTP reach the recipient quickly without any problems.

However, SMTP has some drawbacks when faced with events that were not taken into account when it was invented, mainly because they are problems that did not exist then and were not anticipated. For example, the SMTP protocol has no way of checking if the sender of an email is really who he says he is. If we go back to the 1980s, when the Internet was used by a select group of people, mainly in government agencies and teaching and research centers, this was not a big problem.

Starting in the 1990s, the inability to verify the sender began to be a major problem and what has allowed the continuous SPAM increase and other malicious uses of email, such as virus transfer or email spoofing. For example, a program can search an email inbox and send a virus as an attachment to a person's entire contact list on behalf of that person who is trusted by recipients. Progress has been made to improve the security of the SMTP standard, but it is still a long way from being truly secure.

POP3 and IMAP: storage and organization

The POP standard is the protocol used for the storage and organization of emails. It was designed in 1984 with the idea of ​​allowing users to access a mail server, receive messages and store them in a local folder on their own computer, and be able to disconnect from the Internet to read and write messages. The ability to go offline to read or write was really useful when staying connected to the internet was expensive and paid per minute of connection. Currently most mail servers use POP3, the third version of the POP standard that was developed in 1988, or the IMAP standard.

The IMAP protocol is more modern and offers more possibilities than POP3. For example, it allows you to manage several inboxes, several accesses at the same time or multiple organization criteria. If you want detailed information about each protocol, you can consult the RFC 821 documents.

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