SMTP: create a new davmail.smtpStripFrom boolean property to force From: header removal

git-svn-id: http://svn.code.sf.net/p/davmail/code/trunk@2193 3d1905a2-6b24-0410-a738-b14d5a86fcbd

src/java/davmail/exchange/ExchangeSession.java

@@ -1291,7 +1291,7 @@ public abstract class ExchangeSession {
         convertResentHeader(mimeMessage, "Message-Id");
 
         // do not allow send as another user on Exchange 2003
-        if ("Exchange2003".equals(serverVersion)) {
+        if ("Exchange2003".equals(serverVersion) || Settings.getBooleanProperty("davmail.smtpStripFrom", false)) {
             mimeMessage.removeHeader("From");
         }