It would be great if a teammate could assign a Due Date for when a reply needs to go out for a specific conversation. We could tie in the Due Date with existing SLA rules, or issues notifications if the Due Date passes without a response from the ...
Instead of "From 9 to 5 from Mon to Fri", be able to say "From 9 to 5 from Mon to Fri, except on Dec 25, Jan 1, etc". This allows to take plan for holidays, teammate PTOs, company events, etc.
Custom message order so that the most recent email in a conversation thread is shown at the top
Ability to change the order in which new messages are displayed in a thread. Today, the oldest message is at the top, and the most recent is at the bottom.