The aim of Gajim is to offer a fully functional and easy to handle XMPP-Client. The most important features are:

• Chat-window with tabs or in single windows
• Support for group-chats
• Emoticons, avatars
• Audio- and video-conferences
• File transfer
• Support for several accounts
• Expandable scope of functions due to plugins

Linux Fedora:

sudo dnf install gajim 

Microsoft Windows:

https://gajim.org/downloads.php?lang=de#windows

In the beginning, the so-called Jabber-ID needs to be entered in Gajim:

• Accounts/ +
  • Select option „Ich habe bereits ein Konto, das ich benutzen möchte“ (ENG: “I already have an account, which I would like to use”)
  • Jabber-ID: <username>@xmpp.jade-hs.de
  • Password: Your password

Following settings should be done

• Plugins:
  • OMEMO
  • clickable nicknames
  • message box size
  • Plugin Installer
  • Plugin translations
  • Url image preview

• menu Gajim / settings
  • general
    • appearance of the chat: a window for everything
  • notification
    • show notification if a contact logs in: disabled
  • extended
    • privacy: allow to send messeges of my inactivity: disabled
    • extended configuartion editor / open
      • optional name: print_status_in_chats : Wert: disabled / type: Boolesch
      • optional name: print_status_in_muc / Wert: none / type: text

In the end, you have to restart gajim, that the changes in settings will be shown.

Add chatpartner:

• menu accounts / add contact…
  • JID: type in the Jabber-ID of your chat partner
  • Nickname: name of your chat partner (normally surname and prename)
  • Add

How to activate message encryption:

• In one-on-one chats the messages should be encrypted with end-to-end encryption. This is ensured due to the OMEMO-plugin.
• Activation of the end-to.end encryption:
  • double-click on the chat partner and then click on the locker with the exclamation mark downright and activate OMEMO.