Eva: A system administrator at Acme Corp with extensive experience with Kolab Enterprise
Susy: A project manager at Acme Corp
Robert: Knowledge worker at Acme Corp, works part time from home, is a member of Susy's team
Robert is on a phone call with a client. An invitation to an edit session appears from Susy as a notification in Robert's Roundcube session.
Robert defers the invitation by clicking the "Defer" button in the invitation - including a note as to why.
Susy sees Robert's defer response as a notification along with his message that he is currently on the phone.