Gmail has a really cool system to help you filter and sort messages as they come in. I have many rules in place to help me manage my inbox and a lot of those rules forward a message out based on a given criteria set.
I wish they would make some tiny improvements to this.
The one that seems most needed is an indicator on a thread, to tell you when an email has been forwarded by a rule. When you have a lot of different rules to forward email out, sometimes you're not sure if certain message did indeed get passed on to the right person. The only way to check right now is to: 1. check with the intended recipient or 2. there is no other way.
You can't even look in your sent items because the email message doesn't get sent, instead its just forwarded or redirected.
If an indicator is too much trouble, maybe just drop them into the sent folder like any other message, then I could see if something was forwarded and to whom.