Visual Basic 6.0

Email Received Header Fields

Received emails will contain one or more "Received" header fields at the beginning of the email header. Each SMTP server (along the delivery path) adds a Received header to the top of the incoming message. The delivery route can be ascertained by the sequence of Received headers. There is a good summary of the Received header here.

The following explanation is taken from the reference URL above:

In theory, the value of a Received field is tokenizable. It contains

    1) optionally, a "from" atom followed by an encoded domain name;
    2) optionally, a "by" atom followed by an encoded domain name;
    3) optionally, a "via" atom followed by another atom;
    4) zero or more of the following: a "with" atom followed by another atom;
    5) optionally, an "id" atom followed by either (1) an atom or (2) a < token, an encoded address, and a > token;
    6) optionally, a "for" atom followed by an encoded address;
    7) a semicolon; and
    8) a timestamp. 

In practice, SMTP servers put all sorts of badly formatted information into Received lines. It is probably best for readers to treat everything before the final semicolon as unstructured text, purely for human consumption.

This example demonstrates iterating over each of the Recevied headers and getting the content of each.

Visual Basic 6.0

Dim success As Long
success = 0

Dim email As New ChilkatEmail

' Load a .eml file into the email object.
success = email.LoadEml("/home/users/chilkat/eml/myEml.eml")
If (success = 0) Then
    Debug.Print email.LastErrorText
    Exit Sub
End If

Dim sbHdrName As New ChilkatStringBuilder

Dim i As Long
i = 0
Dim numHeaders As Long
numHeaders = email.NumHeaderFields
Do While i < numHeaders
    success = sbHdrName.SetString(email.GetHeaderFieldName(i))
    If (sbHdrName.ContentsEqual("Received",0) = 1) Then
        Debug.Print "Received: " & email.GetHeaderFieldValue(i)
    End If

    i = i + 1
Loop