I cannot find an overload, that matches your parameters, closest is
Public Shared Function SendMail(ByVal MailFrom As String, ByVal MailTo As String, ByVal Bcc As String, _
ByVal Subject As String, ByVal Body As String, ByVal Attachment As String, ByVal BodyType As String, _
ByVal SMTPServer As String, ByVal SMTPAuthentication As String, ByVal SMTPUsername As String, ByVal SMTPPassword As String) As String
but you cannot pass "text" as attachment and need to specify the BodyType. This overload exisits for backwards compatibilty, I suggest to use one of the subsequent overloads with improved type security.