I use XMPP with OMEMO because:
- It’s reasonably secure
- It’s fast
- Email isn’t either of those
To send a message, use an XMPP client.
My current XMPP address is sky@404.city
If you need an XMPP client, go here and pick one that fits you.
Win/Mac/Nix: https://gajim.org/download/