好长时间没用vb写成程序，现在遇到一个收邮件的问题,大家帮我看看

Question

为什么程序执行完pop3.SendData "USER xxx" & "vbcrlf" 
程序就结束呢？
Private Sub Command1_Click()    Command1.Enabled = False
        
    pop3.RemoteHost = "mail.xxx.net"
    pop3.RemotePort = "110"
    
    pop3.Connect
    Command1.Enabled = True
    
    
    
End Sub
  
Dim Data As String
    pop3.GetData Data, vbString
    Debug.Print Data
    Select Case Left(Data, 1)
        Case "+"
            
            Select Case tag
                Case "conn"
                    tag = "user"
                    pop3.SendData "USER xxx" & "vbcrlf"
                    MsgBox Data
                Case "user"
                    tag = "pass"
                    pop3.SendData "PASS xxx" & "vbcrlf"
                    
                    MsgBox Data
            End Select
        Case "-"
            MsgBox ″错误″ & Data
  
    End Select

Answer 1

更正
Private Sub pop3_DataArrival(ByVal bytesTotal As Long)
    Dim Data As String
    pop3.GetData Data, vbString
    Debug.Print Data
    Select Case Left(Data, 1)
        Case "+"
            
            Select Case tag
                Case "conn"
                    tag = "user"
                    pop3.SendData "USER ayw" & "vbcrlf"
                    MsgBox Data
                Case "user"
                    tag = "pass"
                    pop3.SendData "PASS 7709211102" & "vbcrlf"
                    
                    MsgBox Data
            End Select
        Case "-"
            MsgBox ″错误″ & Data
                   
    End Select
End Sub