[Pistos2]

(I'm not OP) Zulip is good in theory, but I had two problems with it:

1) they had no [simple] means to install it on an existing server (VPS, what-have-you). It assumed (required!) that Zulip would be the only thing on whatever you installed it on. That is, it seemed to assume a container environment (docker, etc.)

B) The public Zulip instance exposed everyone's email address in plain text, ready for easy harvesting.

iii) It's hard to alter the inertia of a team or organization of sufficient size that is already using Slack.

[vishnu_ks]

2) This is fixed. If you are running on-prem you can upgrade from master or wait till the next stable release. https://zulipchat.com/help/restrict-visibility-of-email-addr....

3) Zulip do support importing from Slack. https://zulipchat.com/help/import-from-slack. I don't think there is anything else we can do about this issue.