Every day I send my father a long email with four or five copied newspaper articles. A few days ago, he started seeing the emails in italics, or in very small fonts, or with lines broken up as if someone had inserted a hard CR (carriage return) every few lines.
I am using IE7, with Hotmail. He is using Thunderbird 1.5.0.9 and Firefox 1.5.0.9. He tells me that usually he reads his email in Thunderbird without even opening up the Firefox browser. I have tried sending using Sun System Messenger Express, but he reports the same problems.

Is there some setting he's missing?
Could this be some kind of virus?

I have tried sending my emails to several other friends and relatives using different email software such as Yahoo!, and various different screen resolutions, but they all inform me that my mailings look fine.

Against my better judgement, he's using Norton Security to check his computer for viruses in real-time, plus a weekly scan.

Thank you.