I swear most executives can barely read so you're not doing your career any favors sending them more than 150 characters.
It's called an executive summary because that's the only thing the executive will read of your carefully put together report.
In instances where context is important, I have been including a summary with call to action at the start of the message, then include details below to hopefully eliminate back and forth. It helps me be more clear with my point, and most people once they have an action only use the context for reference later.
The CEO of one firm I worked at wrote emails totally in bullet point format.
Made it much easier to read and you could just reply with:
> bullet point
response
which made life much easier