I have our RHEL 4 Linux servers sendmail configured to relay via an Exchange server. The DS in sendmail.cf has the name of the exchange server. Question #1 - If the Exchange server is down, mail does not remain queued up on the Linux server but rather a reply is sent back to the local sender. How do I configure sendmail so that the mail remains queued until Exhange comes up ? I probably have some misconfiguration here. Question #2 - We have a home-grown app that sends email from a Linux server directly via Exchange (kind of like "telnet exchange 25"). The app. people want to change their code so that it checks if exchange is up and if not then send it to another Linux server and just queue it up there. When exchange is back up then flush the queue. Maybe correct configuration in #1 will address problem #2 ? I've toyed with the "HoldExpensive" options in sendmail.cf and that appears to work, however, is this the correct way to do it ? And do I have to have a dedicated mail server just to hold this ? Thanks.