E-mail, chat, & VoIP : Probably a stupid Outlook Express question

Probably a stupid Outlook Express question

I'm having problems with Outlook Express. I've been a long-time Eudora user; however, the junk mail feature in Eudora was trashing messages that weren't junk, and VetoMail won't work with Eudora, so I've had to go back to Outlook Express. My problem is that some messages will come in looking like a horrible experiment in HTML gone wrong - scrambled code, HTML tags all over the place, etc. It only happens on SOME messages, though, as my newsletters and such come across just fine. I've set all the settings for HTML that I could find in OE, and I have set it to use the Internet Zone and removed the "virus protection" checkmark for attachments. Microsoft's support sites and forums have nothing on the problem, so I don't know if it's just a glitch on my end or what. If anyone can assist me with this it would be greatly appreciated!

Thanks in advance,
-Pete