PureBasic

Extract Linked Domains from an HTML Email

Demonstrates the Chilkat Email.LinkedDomains method, which extracts the domain names from the hyperlinks in an HTML email. Lowercase domains are appended to a StringTable without creating duplicates. This example sets an HTML body with several links and lists the distinct domains.

Background: The set of domains a message links to is a strong signal for spam and phishing analysis — legitimate mail usually points at a few expected domains, while abusive mail often hides links to many unrelated or look-alike hosts. LinkedDomains gives you that de-duplicated list directly. Note it only parses the links; it does not fetch them, so no network request is made.

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IncludeFile "CkEmail.pb"
IncludeFile "CkStringTable.pb"

Procedure ChilkatExample()

    success.i = 0

    ;  Demonstrates the LinkedDomains method, which extracts the domain names from the
    ;  hyperlinks in an HTML email.  Lowercase domains are appended to a StringTable without
    ;  creating duplicates.

    email.i = CkEmail::ckCreate()
    If email.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkEmail::setCkSubject(email, "LinkedDomains example")

    ;  An HTML body containing several hyperlinks.
    CkEmail::ckSetHtmlBody(email,"<html><body>Visit <a href=" + Chr(34) + "https://www.example.com/page" + Chr(34) + ">Example</a>, <a href=" + Chr(34) + "http://sales.contoso.com" + Chr(34) + ">Contoso</a>, and <a href=" + Chr(34) + "https://www.example.com/other" + Chr(34) + ">Example again</a>.</body></html>")

    ;  Extract the linked domains into a StringTable.
    domains.i = CkStringTable::ckCreate()
    If domains.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkEmail::ckLinkedDomains(email,domains)
    If success = 0
        Debug CkEmail::ckLastErrorText(email)
        CkEmail::ckDispose(email)
        CkStringTable::ckDispose(domains)
        ProcedureReturn
    EndIf

    n.i = CkStringTable::ckCount(domains)
    i.i
    For i = 0 To n - 1
        Debug CkStringTable::ckStringAt(domains,i)
    Next


    CkEmail::ckDispose(email)
    CkStringTable::ckDispose(domains)


    ProcedureReturn
EndProcedure