fixed case-sensitivity of user email

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

@@ -84,7 +84,7 @@ public class MailingList implements MessageHandler, ProblemListener {
      * @param state
      */
     public MailingList(String email, String name, String imapHost, int imapPort, String imapUser, String imapPass, String inbox, String smtpHost, int smtpPort, String smtpUser, String smtpPass, int state) {
-        this.email = email;
+        this.email = email.toLowerCase();
         this.name = name;
         this.state = state;
         this.smtp = new SmtpClient(smtpHost,smtpPort,smtpUser,smtpPass,email);
@@ -259,6 +259,7 @@ public class MailingList implements MessageHandler, ProblemListener {
      */
     public static MailingList load(String listEmail) {
         if (listEmail == null) return null;
+        listEmail = listEmail.toLowerCase();
         var ml = cache.get(listEmail);
         try {
             var rs = Database.open()