We've been using Veeam with SmarterMail for several years and have never had the issue you describe. Our SM server is a VMware VM, so I don't know how that matches your environment.

I am not aware of any specific switches that need to be implemented in Veeam as it should already use volume shadow copy which is recommended to avoid JSON file corruption. Is it possible Symantec introduced these issues during your shutdown of it?

I wonder if the backups ran simultaneously and caused the corruption.

When I have some time I'm going to setup robocopy to get up to date data elsewhere... then remove symantec and try veeam as its our prefered/newer solution for backup.

That is quite possible. Veeam won't lock files, but it's possible Symantec still had them locked when Veeam started doing it's work. Please don't hesitate to submit a ticket with us if you end up needing a hand. Have a good one Tim!

We dont use veeam, we use Macrium which also relies on VSS, been using it for the better part of a decade and never had a single issue with it locking up files, causing write issues or corruption.

We have had instances when veeam is performing the backup and it can cause some weird issues with SM, essentially ending up with the backup job never completing, just sat there eating resources, SM would then stop accepting connections etc, suspect it was a VSS issue rather than Veeam itself however we have not experienced the issue with the v5 agent so far. There was no specific pattern for when it would occur so we couldn't track it down to SM, Veeam or VSS. We have not had any corruption issues with Veeam and SM.

Chiming in on this old thread. 

Chris, recently we've been having that exact issue with Veeam and SM. The Veeam VSS service times out and the backup fails. Then within a few minutes we start getting alerts and customer reports of issues with email. Restarting the server just hangs and we have to do a hard reset. This results in JSON corruption. We know what to look for and can fix it quickly, but this is not ideal.

I have a ticket open with Veeam, but they're saying VSS isn't supported with SM and that we should disable that feature in our backup jobs. What's interesting is from the logs I pulled for Veeam I can see that only the C volume is being shadow copied. It's not even touching the volumes SM is using.

I'm just sharing our experience and seeing if anyone else has encountered the same. Chris it would be good to know if you continued to have this issue. Also, I know ST you have stated in the past that you use Veeam with VSS so if you have anything to add on this topic that would be appreciated.