We are planning our migration from 5 to 6, and have read through all of the documentation etc, so are happy with doing a backup and performing an inplace upgrade.
However what does concern me is that if we find a major bug, say missing subfolders or backups are not robust for example. Something that takes a few hours/days/weeks to notice.
We will have a situation where we can't roll back to 5 easily, because there will be a lot of email processed in the interim.
So ideally if we had a way to copy all inbound/outbound email into a "standby" queue, and effectively "replay" these back if we had to restore 5.0.
The process would look something like this(We use VMware):
Do complete backup of the VM.
Disable the NIC to stop network traffic.
Start the VM.
Configure the standby Queues. (perhaps postfix always_bcc?)
Re-enable the NIC.
Send a few test emails and verify they go into the standby queues.
Run a full zm backup
Perform the upgrade.
Sit back and wait for the accolades from users.......yeah I know I am dreaming here....
Then in the unlikely event of a major issue.
Roll back the zm backup, (or copy the queues and then restore the full VM.)
Copy the contents of the standby queues back into the inbound queue.
Let 5.0 reprocess the mail.
Now having just thought this through, that is only going to work for inbound emails, and not for outbound.... sigh.
So, does anyone have a solution for this?