Yep.
I keep everything. I don't delete anything.
On the other hand, if you DON'T want someone to have a record of an incident, TALK ON THE PHONE. Make sure no one is using speaker phone. There is repudiation then. Email is slightly harder to repudiate. Not saying that you'd lie about anything, but if you have a disagreement with anyone, you should handle it over the phone, as email can be construed and BCC'd.