I tried sending an Excel attachment using Mail in 10.4 to one of my clients the other day but she reported back to me that she was unable to open the file. Since she's a client, and not entirely computer savvy, it's been difficult to pinpoint the problem. She's on a PC and is using AOL for email. My Excel attachment has a .xls name and I've checked "Send Windows Friendly Attachment" when sending her the file. Here's where it gets really weird. When my coworker sends her the file (which is stored on central server), she is able to open it. The only difference is that my coworker is on 10.3. We tried this with a few more files and my client could always open them when sent from my coworkers computer, but never from mine. I'd be quite grateful for any suggestions. Thanks!