The normal operation of IMAP is as follows:

1. The email client resolves the IP address of the IMAP server:

As shown in the preceding screenshot, the client establishes a TCP connection to port 143 when SSL/TSL is disabled. When SSL is enabled, the TCP session will be established over port 993.

2. Once the session is established, the client sends an IMAP capability message requesting the server sends the capabilities supported by the server.
3. This is followed by authentication for access to the server. When the authentication is successful, the server replies with response code 3 stating the login was a success:

4. The client now sends the IMAP FETCH command to fetch any mails from the server.
5. When the client is closed, it sends a logout message and clears the TCP session.