backported some code from lang_de branch

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

src/main/java/de/srsoftware/widerhall/data/MailingList.java

@@ -13,8 +13,7 @@ import org.stringtemplate.v4.ST;
 import javax.mail.*;
 import javax.mail.internet.AddressException;
 import javax.mail.internet.InternetAddress;
-import javax.xml.crypto.Data;
-import java.io.*;
+import java.io.UnsupportedEncodingException;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.*;