Also, some companies want to see the full header information in the email if you can give it to them, but not all email providers (ie...yahoo) show the full header information (typically found in the area around the From:/To: lines) in the email by default. The header information is a full list of where the email originated and each stop it took getting to you. They leave the information out because the information it contains is fairly useless for the average computer user, but it can help the companies out by giving them a much more detailed view of where the email started from, thus making it easier for them to track down the person who sent you the phishing email.
Each email program is different, so in some you may need to go into options and select it to show headers, where others may be as simple as clicking a text link (should say something like "Full Header") while you are viewing the email. Not all providers have an option for it, so don't feel like you have to spend a lot of time searching for the option.
Whether you send it with full header information or not, it is important that you never alter the email in any way (that includes adding a comment to the company you forward it to) as they need to see the email in its original form.