Relating to or involving a conference or discussion between parties.
From Latin conferentia (a bringing together, discussion) plus the adjective suffix -al. Conferential describes the nature of conference-based interaction.
This adjective is rare in modern usage, but it perfectly captures what's missing from email—the conferential aspect of looking someone in the eye while disagreeing respectfully.
Complete word intelligence in one call. Free tier — 50 lookups/day.