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Christian Williams said:
Your email is visible to the members on this server. https://github.com/zulip/zulip/issues/11454
If you do not want this to be the case, you need to log in with another email. Sorry for the inconvenience.
I'm not sure why that issue is still open (it may have been forgotten and become stale), but the feature already exists under "Organization permissions". See the help page.
EDIT: (I should have put this in #meta; hopefully it'll be movable soon.)
Ah I see, that's good to know. We'll add it to the guide. Yes, these should have been in meta; it's okay.