Difference Between SMTP and IMAP (with Table)

SMTP and IMAP are two email protocols that are involved in transferring electronic messages. SMTP stands for Simple Mail Transfer Protocol while IMAP stands for Internet Message Access Protocol.

Basically, an email protocol establishes a connection between the sender, email server, and receiver. SMTP is needed to send an electronic message from a sender to an email server, and subsequently carry the message between two email servers.

On the other hand, IMAP is needed to retrieve an electronic message that is stored in an email server.

The difference between SMTP and IMAP is that both are meant for different functions. SMTP is only meant for sending messages while IMAP is meant for managing and retrieving messages.

Comparison Table Between SMTP and IMAP

Parameters of ComparisonSMTPIMAP
Full formSMTP is an acronym for Simple Mail Transfer Protocol.IMAP is an acronym for Internet Message Access Protocol.
MeaningSMTP is an email protocol that establishes a way for electronic messages to be transferred from a sender to an email server, and subsequently between two email servers.IMAP is an email protocol that establishes a way of managing and retrieving electronic messages from an email server.
FunctionThe function of SMTP is only to send electronic messages to a server or between servers.The function of IMAP is to manage and retrieve electronic messages from a server.
TransferSMTP transfers electronic messages from a client to a server as well as between two servers.IMAP transfers electronic messages only from an email server to a client.
PortsSMTP works on port 25 (standard for mail transfer), port 465 (not compliant with RFC), port 587 (TLS encrypted), and port 2525 (not an official port but supports almost every email service).IMAP works on port 143 (default port without encryption) and port 993 (secure SSL/TLS port that is often called IMAPS).

What is SMTP?

SMTP is a text-based industry-standard protocol for email services. It establishes a mechanism for the transfer of electronic messages from a sender to an email server, as well as between two email servers. SMTP stands for Simple Mail Transfer Protocol. It is only meant to ‘send’ messages.

In an SMTP server, an SMTP client sends commands in the form of texts such as HELLO, MAIL, RCPT, etc. These are replied to by SMTP servers in the form of numeric completion codes such as 220, 250, 354, and so on. This work-flow is used to transfer electronic messages from one party to another.

SMTP mechanisms were developed during the 1970s. Usenet, a communication network that came during the same period had many similarities with SMTP servers. Subsequently, during the 1980s, SMTP gained popularity as it was complimentary to UUCP mail (Unix to Unix Copy Program).

At present time, SMTP supports servers including IceWarp, Sendmail, Exim, Postfix, MagicMail, MailEnable, and HMailServer. The clients that it supports include Mozilla Thunderbird (after version 82.0) and NMH (after version 1.7).

smtp message flow

What is IMAP?

IMAP is a communication standard protocol for email services. It establishes a mechanism for retrieving electronic messages from an email server. These messages are always stored on the server. When the receiver starts the application and picks a message, the protocol automatically downloads it.

RECOMMENDED
Difference Between Dual-Core and Quad-Core (With Table)

IMAP is only meant to manage and receive messages on demand. The transfer is between a server and a client only, as opposed to SMTP. IMAP server responses are of three categories – Status Responses (OK, BYE, BAD, NO), Server Data (CAPABILITY, EXIST, FETCH), and Command Continuation Request.

Almost every implementation of IMAP allows multiple devices to connect with the server simultaneously. However, IMAP can be compared with POP3 for its communications service. POP3 stores all the electronic messages in one digital ‘mailbox’. This is downloaded entirely when the receiver opens the application.

Originally, IMAP was a remote access mailbox protocol that was designed by Mark Crispin. After going through many alterations and upgrades, the latest version IMAP2bis was released. It was later re-named IMAP4 to avoid confusion.

imap

Main Differences Between SMTP and IMAP

  1. SMTP is an acronym for Simple Mail Transfer Protocol and IMAP is an acronym for Internet Message Access Protocol.
  2. SMTP is a mechanism that establishes a protocol for electronic messages to be sent to an email server or between servers while IMAP is a mechanism that retrieves electronic messages from email servers.
  3. SMTP is only meant for ‘sending’ while IMAP is meant for managing and retrieving messages.
  4. SMTP can transfer messages from a client to a server as well as between two servers. On the contrary, IMAP can only transfer messages from a server to a client.
  5. SMTP works on port 25 (standard for mail transfer), port 465 (not compliant with RFC), port 587 (TLS encrypted), and port 2525 (not an official port but supports almost every email service). On the other hand, IMAP works on port 143 (default port without encryption) and port 993 (secure SSL/TLS port that is often called IMAPS).

Conclusion

SMTP and IMAP are required together as protocols for sending and receiving messages. These act as a connection between the sender, email server, and receiver. While SMTP is meant for pushing the message, IMAP is meant for retrieving it.

SMTP is one of the most prevalent servers to be used at present. However, IMAP competes with POP3, which is a communication protocol that stores all the messages in a mailbox and downloads the messages. This allows the client to access the messages offline as well.

What sets IMAP apart, is its capacity for multiple logins. So, if a client needs to access mail from different devices, IMAP works perfectly. POP3 is perfect for clients who have low or unstable internet connections.

References

  1. https://www2.rivier.edu/faculty/vriabov/Information-Security-SMTP_c60_p01-23.pdf
  2. http://www.hjp.at/doc/rfc/rfc2595.html