add alternative when loading the username

enzevalos_iphone/MailSession.swift

@@ -525,7 +525,11 @@ class MailSession {
         self.sessionType = sessionType
         if let username = UserManager.loadUserValue(Attribute.accountname) as? String {
             self.username = username
-        }else {
+        }
+        else if let username = UserManager.loadUserValue(Attribute.userAddr) as? String {
+            self.username = username
+        }
+        else {
             throw MailServerConnectionError.AuthenticationError
         }
         if let pw = UserManager.loadUserValue(Attribute.userPW) as? String {