Email is an information silo

“Oh, you weren't in the meeting. Let me forward you the minutes so you can catch up” ... “Ah, you weren't included in the email conversation. I'll send it you, and you can read the entire conversation so you know what has happened so far.” ... “Oh, we decided this some time ago, before the last email migration. Unfortunately our older emails are no longer accessible.”

Email is an information silo. If you use it to store knowledge that has long-term value (decisions, logs, discussions, whatever else), it'll end up hurting you soon enough.