e is used when the user accesses the mails through a system away from the local workstation, SO that the mail can be read and maintained for later retrieval and organizing. However POP3 has several limitations. C. Internet mail access protocol, version 4 (IMAP4): It is a mail access proto- col. IMAP4 is a powerful and complex mail access protocol used to handle the transmission of email. Using IMAP4 the user can create the mailbox hierarchy in a folder for e-mail storage or even create, delete, or rename the mailboxes on the mail server. In cases where the bandwidth is low and the e-mail contains multimedia with high bandwidth requirements, the user can partially download the e-mail through IMAP4. It is also possible to check the e-mail header or search for a string of characters in the e-mail content before downloading. 29.4 User Agent The user agent is a component of the electronic mail system. It is a software package that performs the following basic functions: Composing messages: The e-mail messages to be sent out are composed by the user agent. Some user agents provide a template on the screen that has to be filled in by the user while other user agents have a built-in editor that can perform sophisticated tasks like spell check, grammar check, and SO on. The user can create his message in a word processor or text editor that can be imported or cut and pasted to the user agent. Mail Communication Reading messages: The incoming messages are read by the user agents. A user agent (when invoked, checks the mail in the incoming mailbox) referred to as an inbox. For each of the received mail, the user agent shows a one-line sum- mary with fields like the number field, a flag indicating whether the mail has been read and replied to or read but not replied to, sender name, subject field if subject line in the message is not empty, and message size. Replying to messages: The user agent allows the user to send a reply message to the original sender of the message or to all the recipients such that the reply message c