Off The Record messaging
Implement off-the-record messaging (https://otr.cypherpunks.ca/)
Ticket for this feature can be followed here: https://mattermost.atlassian.net/browse/MM-669
Please add a OTR feature to mattermost. From my point of view, this is a must have feature...especially if you would like to replace an existing jabber service.
This is something we're investigating, and currently blocking us:
Some private chats should by default be OTR so that not even DB admins can read them, for example all chats between specific people.
Having no search available for such private messages is understandable and OK for such private messages.
There is also OMEMO, an extension to XMPP which improves on OTR encryption by allowing group chat encryption and forward secrecy.
Based on the same Axolotl protocol as Signal.
I'd suggest using Signal's improved OTR encryption protocol that amongst other things allowed encrypted *group* chats.
They've already implemented their protocol on WhatsApp so asking them directly may also be useful to help implement it.