We have O365 configured to use EV SMTP archiving (on prem) for Journal messages. In O365 you can/need to define an Alternate Recipient. This AR is only used if the connection between O365 and the on-prem target smtp addresses is broken (for whatever reason). As example, the normal route is to send O365 journal messages to Journal@gertjan.net. If that connection breaks, the journal messages need to be send to Journalbackup@alink.net
when using this, the messages which go to journalbackup are NEW messages (basically NDR's), having the actual Journal Message as an attachment. This means you cannot simply forward these messages to firstname.lastname@example.org, as the EV SMTP server would not recognize the target-email-address. You will therefor need to somehow extract the attachment, and then send that as a message to the target smtp address.
Does anyone have any experience with that? What did you use to configure the AR? We've been looking at Postfix, but that proved to be challenging. Do you use the AR, or do you rely on O365 being able to re-astablish the connection quick?