diff --git a/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java b/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java
index 4f0d3b0..1a4d1a1 100644
--- a/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java
+++ b/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java
@@ -22,10 +22,10 @@ import org.w3c.dom.DOMException;
 import org.w3c.dom.Document;
 import org.w3c.dom.Element;
 
+import de.hsadmin.core.model.HSAdminException;
 import de.hsadmin.core.model.Transaction;
 import de.hsadmin.core.util.IPv6Trick;
 import de.hsadmin.mods.email.EMailAddress;
-import de.hsadmin.mods.pac.Pac;
 import de.hsadmin.mods.user.UnixUser;
 
 public class AutoconfigAutodiscoverServlet extends HttpServlet {
@@ -47,55 +47,31 @@ public class AutoconfigAutodiscoverServlet extends HttpServlet {
 			resp.sendError(HttpStatus.SC_BAD_REQUEST);
 			return;
 		}
-		final String localpart = addrParts[0];
-		final String domain = addrParts[1];
-		final Transaction transaction = new Transaction("autoconfig");
-		final EntityManager em = transaction.getEntityManager();
-		final Query emailQuery = em.createQuery("SELECT addr FROM EMailAddresses addr WHERE addr.localpart = :localpart AND addr.domain.name = :domain AND ( addr.subdomain IS NULL OR addr.subdomain = :subdomain)");
-		emailQuery.setParameter("subdomain", "");
-		emailQuery.setParameter("domain", domain);
-		emailQuery.setParameter("localpart", localpart);
-		final Object emailResult = emailQuery.getSingleResult();
-		if (emailResult == null) {
-			transaction.close();
-			resp.sendError(HttpStatus.SC_BAD_REQUEST);
-			return;
-		}
-		final EMailAddress emailAddress = (EMailAddress) emailResult;
-		final Query mboxQuery = em.createQuery("SELECT mbox FROM UnixUsers mbox WHERE mbox.name = :target");
-		final String target = emailAddress.getTarget();
-		if (target == null || target.length() < 5 || (target.length() > 6 && target.charAt(5) != '-')) {
-			transaction.close();
-			resp.sendError(HttpStatus.SC_BAD_REQUEST);
-			return;
-		}
-		mboxQuery.setParameter("target", target);
-		final Object mboxResult = mboxQuery.getSingleResult();
-		if (mboxResult == null) {
-			transaction.close();
-			resp.sendError(HttpStatus.SC_BAD_REQUEST);
-			return;
-		}
-		final UnixUser mbox = (UnixUser) mboxResult;
-		final Pac pac = mbox.getPac();
-		final String pacDomain = pac.getName() + ".hostsharing.net"; 
-		final String userName = mbox.getName();
+		String uniqueMailbox = null;
 		try {
-			DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
-			DocumentBuilder builder = builderFactory.newDocumentBuilder();
-			Document document = builder.newDocument();
-			Element clientConfig = document.createElement("clientConfig");
+			uniqueMailbox = getUniqueMailbox(emailAddr);
+		} catch (HSAdminException e) {
+			throw new ServletException(e);
+		}
+		final String pacName = uniqueMailbox.substring(0, 5);
+		final String pacDomain = pacName + ".hostsharing.net"; 
+		final String userName = uniqueMailbox;
+		try {
+			final DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
+			final DocumentBuilder builder = builderFactory.newDocumentBuilder();
+			final Document document = builder.newDocument();
+			final Element clientConfig = document.createElement("clientConfig");
 			clientConfig.setAttribute("version", "1.1");
 			document.appendChild(clientConfig);
-			Element emailProvider = appendElementWithAttribute(document, clientConfig, "emailProvider", "id", "hostsharing.net");
+			final Element emailProvider = appendElementWithAttribute(document, clientConfig, "emailProvider", "id", "hostsharing.net");
 			appendElementWithText(document, emailProvider, "domain", "hostsharing.net");
-			Element incomingServer = appendElementWithAttribute(document, emailProvider, "incomingServer", "type", "imap");
+			final Element incomingServer = appendElementWithAttribute(document, emailProvider, "incomingServer", "type", "imap");
 			appendElementWithText(document, incomingServer, "hostname", pacDomain);
 			appendElementWithText(document, incomingServer, "port", "993");
 			appendElementWithText(document, incomingServer, "socketType", "SSL");
 			appendElementWithText(document, incomingServer, "username", userName);
 			appendElementWithText(document, incomingServer, "authentication", "password-cleartext");
-			Element outgoingServer = appendElementWithAttribute(document, emailProvider, "outgoingServer", "type", "smtp");
+			final Element outgoingServer = appendElementWithAttribute(document, emailProvider, "outgoingServer", "type", "smtp");
 			appendElementWithText(document, outgoingServer, "hostname", pacDomain);
 			appendElementWithText(document, outgoingServer, "port", "465");
 			appendElementWithText(document, outgoingServer, "socketType", "SSL");
@@ -109,7 +85,6 @@ public class AutoconfigAutodiscoverServlet extends HttpServlet {
 		} catch (ParserConfigurationException e) {
 			throw new ServletException(e);
 		}
-		transaction.close();
 	}
 	
 	/**
@@ -153,4 +128,42 @@ public class AutoconfigAutodiscoverServlet extends HttpServlet {
 			throw new ServletException(e);
 		}
 	}
+	
+	private String getUniqueMailbox(final String email) throws HSAdminException {
+		final String[] addrParts = email.split("@");
+		if (addrParts.length != 2) {
+			throw new HSAdminException("email address not valid");
+		}
+		final String localpart = addrParts[0];
+		final String domain = addrParts[1];
+		final Transaction transaction = new Transaction("autoconfig");
+		final EntityManager em = transaction.getEntityManager();
+		final Query emailQuery = em.createQuery("SELECT addr FROM EMailAddresses addr "
+			+ "WHERE addr.localpart = :localpart AND addr.domain.name = :domain AND ( addr.subdomain IS NULL OR addr.subdomain = :subdomain)");
+		emailQuery.setParameter("subdomain", "");
+		emailQuery.setParameter("domain", domain);
+		emailQuery.setParameter("localpart", localpart);
+		final Object emailResult = emailQuery.getSingleResult();
+		if (emailResult == null) {
+			transaction.close();
+			throw new HSAdminException("email address unknown");
+		}
+		final EMailAddress emailAddress = (EMailAddress) emailResult;
+		final String target = emailAddress.getTarget();
+		if (target == null || target.length() < 5 || (target.length() > 6 && target.charAt(5) != '-')) {
+			transaction.close();
+			throw new HSAdminException("no unique mailbox found");
+		}
+		final Query mboxQuery = em.createQuery("SELECT mbox FROM UnixUsers mbox WHERE mbox.name = :target");
+		mboxQuery.setParameter("target", target);
+		final Object mboxResult = mboxQuery.getSingleResult();
+		if (mboxResult == null || !(mboxQuery instanceof UnixUser)) {
+			transaction.close();
+			throw new HSAdminException("no unique mailbox found");
+		}
+		final UnixUser mbox = (UnixUser) mboxResult;
+		final String uniqueUsername = mbox.getName();
+		transaction.close();
+		return uniqueUsername;
+	}
 }