If your company use Microsoft 365 / Microsoft Exchange for the emails in Kolleno, it can happen that the thread is missing from the email when you reply or forward it.
This happens because someone in your company has connected to the inbox outside of Kolleno and either:
Deleted the original email you are replying or forwarding
Moved the email to another folder
For the Kolleno integration to work correctly, please do not connect to the inbox other than outside Kolleno.