In normal case, the emails will spool up on our server for 5 days. Emails will be forwarded to your mail server automatically while your mail server come back online. If your mail server is going to be down for more than 5 days, then you definitely want to turn on mail rescue mode to access/reply your emails. Emails will be kept for 30 days at mail rescue server. If you need more than 30 days, you have to contact us to extend the period.