The header of an e-mail message contains different fields. Each field specifies some information regarding the e-mail message. For example, Sender: field indicates the email address of the sender. Date: field indicates when and on what date the mail is sent by the sender.
• Received: is one of the header lines of the mail message header.
• A mail message header may contain more than one Received: fields.
• Received: field is used to indicate the sequence of SMTP servers through which the mail message traveled before reaching the receiver’s mail box.
• When a mail message is received, SMTP adds host name of the source or IP address of the source and time stamp in the Received: field.
• Consider that a user with an .edu email address sent a mail message. Then examine the examine the Received: field in the mail message header.
• If the header contains multiple Received: headers, examine the last Received: field of the header, since the last Received: field contains the IP address of the sender’s host.
Consider the following example Received: header line:
From the above header field, it can be determined that 126.96.36.199 is the IP address of the Host from which the mail message was sent.
Therefore, the IP address of sender’s host can be determined, if the sender sent the message from the .edu email address.
• Only when a mail is sent from SMTP environment, the sender’s host name or IP address of the sender’s host is included in the Received: header line.
• Some mail services like gmail are web-based. When a sender sent the mail message from the web-browser (non-SMTP environment), the e-mail message is delivered from the sender’s browser to sender’s mail server using HTTP protocol rather than using SMTP protocol.
• Thus, the IP address of the sender’s host is not included in the Received: field.
Hence, when a user send’s a message from the gmail account, gmail server do not display the IP address of sender’s host in Receiver: field of the mail message header.
Therefore, the IP address of the sender’s host can’t be determined if the sender sent the message from the gmail account.
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