A calendar that knows which mail the appointment came from
An appointment without its context is an entry with a time on it. An appointment with the mail attached is preparation.

From a sentence to an entry
BoxBee recognises proposed times in the text, even when no invitation file is attached. "Does Tuesday at 2pm at our office work for you" becomes a proposal with date, time and place that you accept with one click.
Attached invitations are handled normally, as are cancellations and reschedules.
The link is the point
The calendar entry says which message it came from. If you want to read up thirty minutes before the meeting, the whole thread is one click away instead of somewhere in search.
It works the other way too: on the message you can see that it turned into an appointment.
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Keep reading
Arriving mail is grouped by kind and urgency before you ever see it.
A draft in the right language and the tone you configured, ready to edit.
A morning summary with the open items pulled out of it.
Every message, attachment and appointment for one matter, bundled.