You are right, of course, though this may seem to conflict with my original comment. One way to reduce email size is to put context information into reference documentation. (Or other substitutes, like Github issues, JIRA, design docs, requirements, operational run books, etc.)

One thing that may not work very well is depending on Slack channels or other chat systems for context. It's fine for an on-going issue but does not work for general information. Important topics are just too hard to find later.