DAV: Another email address failover

git-svn-id: http://svn.code.sf.net/p/davmail/code/trunk@2302 3d1905a2-6b24-0410-a738-b14d5a86fcbd

src/java/davmail/exchange/dav/DavExchangeSession.java

@@ -640,6 +640,9 @@ public class DavExchangeSession extends ExchangeSession {
                 buffer.append(alias);
                 if (alias.indexOf('@') < 0) {
                     buffer.append('@');
+                    if (hostName == null) {
+                        hostName = "mail.unknown.com";
+                    }
                     int dotIndex = hostName.indexOf('.');
                     if (dotIndex >= 0) {
                         buffer.append(hostName.substring(dotIndex + 1));