(Visual Basic 6.0) Reading Unread POP3 Email

The POP3 protocol cannot determine which emails are "unread," and pure POP3 servers do not store this information. Servers like Exchange Server, offering both POP3 and IMAP interfaces, do contain read/unread data, but it's only accessible through IMAP. Email clients like Outlook and Thunderbird store read/unread statuses on the client side. The example demonstrates using UIDLs to track and manage "unread" emails.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Dim success As Long
success = 0

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' The mailman object is used for receiving (POP3) 
' and sending (SMTP) email.
Dim mailman As New ChilkatMailMan

' Set the POP3 server's hostname
mailman.MailHost = "pop.example.com"

' Set the POP3 login/password.
mailman.PopUsername = "***"
mailman.PopPassword = "***"

' Keep a records of already-seen UIDLs in hash table serialized to an XML file.
Dim seenUidlsPath As String
seenUidlsPath = "c:/temp/seenUidls.xml"

Dim sbXml As New ChilkatStringBuilder
Dim htSeenUidls As New ChilkatHashtable
Dim fac As New CkFileAccess
If (fac.FileExists(seenUidlsPath) = 1) Then
    success = sbXml.LoadFile(seenUidlsPath,"utf-8")
    If (success = 0) Then
        Debug.Print sbXml.LastErrorText
        Exit Sub
    End If

    success = htSeenUidls.AddFromXmlSb(sbXml)
End If

' Get the complete list of UIDLs on the mail server.
Dim stUidls As New ChilkatStringTable
success = mailman.FetchUidls(stUidls)
If (success = 0) Then
    Debug.Print mailman.LastErrorText
    Exit Sub
End If

' Build a list of unseen UIDLs
Dim stUnseenUidls As New ChilkatStringTable

Dim uidl As String
Dim i As Long
i = 0
Dim count As Long
count = stUidls.Count
Do While i < count
    uidl = stUidls.StringAt(i)
    If (htSeenUidls.Contains(uidl) <> 1) Then
        success = stUnseenUidls.Append(uidl)
    End If

    i = i + 1
Loop

If (stUnseenUidls.Count = 0) Then
    Debug.Print "No unseen emails!"
    Exit Sub
End If

' Download the unseen emails, adding each UIDL to the "seen" hash table.
Dim email As New ChilkatEmail

count = stUnseenUidls.Count
i = 0
Do While i < count
    ' Download the full email.
    uidl = stUnseenUidls.StringAt(i)
    success = mailman.FetchByUidl(uidl,0,0,email)
    If (success = 0) Then
        Debug.Print mailman.LastErrorText
        Exit Sub
    End If

    Debug.Print i
    Debug.Print "From: " & email.From
    Debug.Print "Subject: " & email.Subject

    ' Add this UIDL to the "seen" hash table.
    success = htSeenUidls.AddStr(uidl,"")

    i = i + 1
Loop

success = mailman.Pop3EndSession()

' Update the "seen" UIDLs file.
sbXml.Clear 
success = htSeenUidls.ToXmlSb(sbXml)
success = sbXml.WriteFile(seenUidlsPath,"utf-8",0)
If (success = 0) Then
    Debug.Print sbXml.LastErrorText
    Exit Sub
End If

Debug.Print "Success."