We're using a relay host with a primary and sec. internet connection with two diffrent providers, when we switch to the secondary the relay host the mta reports correctly "Access denied (in reply to RCPT TO command)"

Is there some way to let zimbra keep the messages in the queue until we switch back? or somehow input two relay hosts so that zžimbra tries one or the other? - without give the "Access denied" error?

Thanks in advance for any ideas