It would be nice to be able to reply to email notifications about comments/messages and have that reply automatically get sent to the client.

Or, it would be nice to click a button or link in the email notification and have it open up the comment/message in the app.

Often, in the mobile app, I try to find the notification and it will say "this item is no longer available" and then I either have to spend time scrolling through the client's calendar to find where they commented or I have to get on the computer to answer them.