The first thing to mention is that you should be on the most recent release of ZCS, now! The second is that you should look at some of the wiki articles and forum threads on this topic and if you have any questions then ask again. BTW, you've posted this in the wrong forum, I'll move it.

Is it possible to upgrade in one step from 8.7.6_GA1776 Foos to zcs-8.8.9_GA_2055 ? Did you read the Release Notes (you should)? My system run on a virtual machine ubuntu 16.04 LTS on a proxmox cluster. I have only one zimbra server with proxy enable. (OSE version) For the upgrade is the "Zimb...

Yes, they're the only additional repositories at this stage. If you plan to use redis then a more recent version should be used and I've also added details to the wiki article.

I've updated the wiki with information about the repository but do feel free to make any changes to the wiki article you deem necessary, it is accessible to everyone to edit.

I guess if this is your hosting provider then this is the reason: https://ericasadun.com/2018/05/15/the-f ... layer-com/

Why are you not sending mail directly to other internet servers?

You can use whichever one you like, if you have that many users you can either use the NE version (with full support) or the OSS version with the ZeXtras package (either from Zimbra or ZeXtras). I'd suggest you look at the product details and comparisons on the main Zimbra web site.

If you're running two mail servers on the same LAN then you'll need a Split Domain setup, full details in the wiki article on the subject.

The rspamd is only for those who admin this server full time, not the part time guy like myself. It's way over most peoples heads. Not really, I don't do this for a living and I'm just a self taught home user of Zimbra so I'm no expert on any of this. If I can do it then anyone can. ;) Update: Now ...

Yeah, but this will not remove the link "Forget Password [Beta]" on login screen, right ? I've no idea as I don't use it. And why we have " Stable " release of zimbra with " Beta " feature, what does this mean ??? Stable but potentially buggy or buggy but potentially s...