socket发邮件的问题(50分)

用socket发送电子邮件时发生下面的错误，请问各位是什么意思

smtp error:500 error :bad syntax

源码
Private Sub Command6_Click()
winsock1.Connect Trim$("smtp.163.com&quot, 25

m_State = MAIL_CONNECT

End Sub

Dim strServerResponse As String

Dim strResponseCode As String

Dim strDataToSend As String
winsock1.GetData strServerResponse

strResponseCode = Left(strServerResponse, 3)

If strResponseCode = "250" Or strResponseCode = "220" Or strResponseCode = "354" Then

Select Case m_State

Case MAIL_CONNECT


m_State = MAIL_HELO

strDataToSend = Trim$("f19881021@163.com&quot

'

'获取信箱名

strDataToSend = Left$(strDataToSend, InStr(1, strDataToSend, "@&quot - 1)

'向服务器发送HELO命令

winsock1.SendData "HELO " & strDataToSend & vbCrLf

'

Case MAIL_HELO

'

'改变当前进程的状态

m_State = MAIL_FROM

'

'向服务器发送 MAIL FROM命令

winsock1.SendData "MAIL FROM: " & Trim$("f19881021@163.com&quot & vbCrLf



Case MAIL_FROM

'

'改变当前进程的状态

m_State = MAIL_RCPTTO

'

'

winsock1.SendData "RCPT TO:" & Trim$("f19881021@163.com&quot & vbCrLf


'

Case MAIL_RCPTTO

'

'改变当前进程的状态

m_State = MAIL_DATA

'

'向服务器发送DATA命令

winsock1.SendData "DATA" & vbCrLf



Case MAIL_DATA

'

'改变当前进程的状态

m_State = MAIL_DOT

'

'现在我们可以开始发送邮件正文

'文本的每一行必须以vbLf结尾

'记住不是vbCrLf

'

'发送邮件主题

winsock1.SendData "Subject:" & "tt" & vbLf




Dim varLines As Variant

Dim varLine As Variant

'

'解析邮件以获得行（VB6适用）

varLines = Split("pp", vbCrLf)

'

'发送每一行邮件

For Each varLine In varLines

winsock1.SendData CStr(varLine) & vbLf

'

Debug.Print CStr(varLine)

Next

'

'向服务器发送一个小数点告诉服务器邮件发送完毕。

winsock1.SendData "." & vbCrLf

'

Debug.Print "."

'

Case MAIL_DOT

'改变当前进程的状态

m_State = MAIL_QUIT

'

'向服务器发送QUIT命令

winsock1.SendData "QUIT" & vbCrLf



Case MAIL_QUIT

'

'断开连接

winsock1.Close

'

End Select


Else

'

'如果服务器返回一个错误的代码就断开连接并提示用户

'

winsock1.Close

'

MsgBox "SMTP Error: " & strServerResponse, vbInformation, "SMTP Error"

'

End If




End Sub