AOL?
A long shot, but...
Does Glide Snr use the AOL client for email by any chance? I remember some time back discovering that if I used this, embedded files and attachments randomly didn't embed or attach. And this only to some recipients, too, which added more confusion.
After much Googling & forum-ing I discovered that this was a known glitch, cured by sending the mail as .txt not as html.
Nothing lost in that way (I believe) since I started using a non-bastardised mail client.
Any help?