Can't forward mail to my wife

My wife has an older iMac, the last one with the older keyboard. She couldn't upgrade to Mountain Lion when I did.

She asked me to order a product from Amazon and forward the receipt to her. Her e-mail is a dot.mac account, mine is not.

She didn't receive it. I re-sent it 4 times without any sign that it wasn't getting through. I added a couple of lines by myself. I finally got it through with a couple of lines and a changed heading.

Does her dot.mac e-mail have an internal spam filter that stopped the earlier messages from going through - without notifying me? My messages aren't in her computer's spam filter.