Security & performance issues (60,000 user):

- Don't support or guide how to integrate with MFA (Multi-factor Authentication)

- Backup & Recovery for 60 Tb email data is hard (60,000 users * 1 Tb/user); no effective solution for backup & recovery for such a case.

- Don't support DLP (Data Loss Prevention) solution.

- HA (High Availability): just support at the server (VMs) layer, don't support at the service layer.

- It is hard to upgrade ZCS 8.0.9 to ZCS 8.8.15 OSE .

It's a big solution for us since internal communication is a must in our organization. We use Zimbra for our internal communication as a whole.

I would like to see a Microsoft schedule function added. In addition, some additional appearance and convenience features would be nice.

When my clients moved from POP3 to IMAP and ActiveSync, they were able to port the complete mailbox. Additionally, Zimbra allows them to centrally manage and store all their emails.

The calendar is a quite useful organizational tool. We also created a lot of accounts for special needs, since we can have as many as we want.

It is the best open source collaboration suite that I know, because it provides high availability and more performance than the other solutions.

We can control all the data in my IT infrastructure.