Service Name is a name you have given to this IMAP4 server. The name doesn't matter. It is used in the settings (in the service tree at the left of this page) and in any error messages.
The Bindings section is described in the Service Bindings topic.
The Encryption option lets you specify how connections to this IMAP4 service are encrypted. This is only available when an SSL certificate is installed; It can be None/STARTTLS, STARTTLS or SSL. IMAP4 supports two types of encryption, STARTTLS and SSL.
STARTTLS is the standard method. With this method, connections are usually made on the standard port (143). The server indicates to the IMAP4 client that encryption is available, and the client sends a STARTTLS command to switch the session from plain text to the encrypted mode. No sensitive data (authentication details, message details, etc) is transmitted while the session is in plain text mode. None/STARTTLS means that VPOP3 offers encryption to the client, but will allow unencrypted connections. STARTTLS means that VPOP3 offers encryption to the client, and requires it to be used.
SSL is a deprecated method. With this method, the connection is made on a port other than port 143 (usually port 993) and starts off encrypted. This means that the IMAP4 client must know that the session is encrypted before it connects, otherwise it won't be able to establish a connection successfully.
Bandwidth Throttling allows you to set limits on how fast data will be transferred through this SMTP service. This allows you to prevent it taking up all your available bandwidth. See the Bandwidth Throttling topic for more information.
The Log data for this service option tells VPOP3 to log session data to a log file IMAP4SVR.LOG (see the Diagnostics settings for more information. It is equivalent to turning on 'Log IMAP4 Server Connections' on that page).