It is an email server. You can set up some kind of system that “catches” incoming email while you take your hardware offline and replace it. Your internal users

It is an email server. You can set up some kind of system that “catches” incoming email while you take your hardware offline and replace it. Your internal users won’t be able to send or receive emails but anyone outside the organization would be none the wiser that your system was down. If you notify ahead of time and can keep downtime to under an hour, will it matter?