Gobbledegook in emails

[#1]

Hi - I get an email newsletter from a well known organisation that is often full of gobbledegook - ie code-like stuff with squares where apostrophes should be etc. It makes it really difficult to read, and often I just don't bother.
Now, someone has just told me that one of my emails to him contained the same sort of rubbish -ie codey sort of stuff and I certainly wasn't aware of this when sending the email.
Anyone know what causes this code to appear? What can I do to stop it?
I'm using a standard Windows set up with OE6 on a PC as was my recipient.
Is it to do more with the recipient's set up than the sender's?
Thanks all 

[#2]

Hmm.  Maybe the sender has sent the email in HTML format whereas you have Outlook Express set to read the emails in plain text format?

[#3]

Thanks James - I just checked my settings in OE and I have not checked the 'read all messages in plain text' box?

[#4]

Could be the character encoding is different between you and them - i.e. they use UTF-8 and you use ISO-8859-1 (Western European) where character codes differ.
Try changing the font setting in OE under Tools -> options -> read tab then fonts at the bottom