Receiving incomplete e-mails

I have been receiving e-mails from a friend. She simply forwards me an e-mail and I get half way thru the e-mail and it stops. Then there is an advertisement for Yahoo (in this case). Usually she will forward me jokes, I read the beginning and then the punch line is not there. I have asked her to forward them as attachments, I do get them OK when she does this. Now she says that others on the mailing list complain when they are sent as attachments. Only those using my ISP are having this problem. I don’t think that it is my ISP, because noone else sends me half e-mails. Any suggestions. Thanks in advance.