Some users have been confused by the new control for forwarding messages.
When you click on Forward, you now see two choices for how you would like to forward your message. These choices have always existed, but you could only change them in the Preferences and then use the same selection all the time. This didn't meet the needs of many users, so we've exposed this option on the compose toolbar. For now you must make a selection each time you want to Forward a message. We will be improving this soon to give the best of both worlds, where you can change the choice inline, or use a single click to use your default choice.
Here's what the two selections mean:
Inline text - this means that the original message text from the sender will be copied into your outgoing message body, and you will see it below what you are typing. This allows easy reference to what the sender said when you are responding to it. This option is most appropriate for regular message correspondence.
As attachment - this is the default forwarding type used by some other webmail services. It means that the original message will be sent along with your message, but as a file attachment. The recipient will not see the forwarded message in your message body, but will need to click on the attached file to view the original message. And if that message was re-forwarded several times, the reader might see a common "nesting" effect where you have to click down through several layers to get to the original. This is all controlled by how each subsequent sender handles the message. In the case of complex HTML emails with formatting and inline images, particularly newsletters, jokes with pictures, and things copied from web pages, you are safest using the "As Attachment" option to make sure your recipient gets the exact original message displayed as intended.
In both cases, any file attachments that came with the message you received and are now forwarding, are resent along with the new message. Don't be confused by inline images that are actually remote links retrieved at viewing time only, those files are not included in the original message and not forwarded in your message. Depending on how the original sender set them up, they may or may not go through.
In most cases your selection of inline text or attachment has no effect on how attachments to the original message are handled. In some cases, depending on how well-behaved the email program used by the sender was, you may need to use "As attachment" in order to make sure all of the original content and files are included in your Forward. One major Web Mail service in particular seems to have this problem with their outgoing messages. So if you get reports of recipients not receiving your forwarded attachments, use the "As Attachment" option. Note that this potential problem only applies to forwarding a message already sent to you. When you create an original message and attach a file to it, that file will always be correctly sent to the recipient.
There have been a few reports from users with old browsers that the forwarding selector doesn't work for them. The oldest browsers we test on and support are IE 5.5, Safari 1.3, and Firefox 1.5. On all other browsers (plus these) we test the most recent versions. If you are having trouble with a supported browser, try clearing your browser cache (delete temporary Internet files) and then restart your browser. If that fails, see if there is an update to your browser available for your operating system.