Email types on V500 (525/600)

What types of e-mail message format can the phone support?
Having just started to use the facility to retrieve e-mails
(using POP3), I am having difficulty viewing certain messages.

So far, I am able to read all test messages sent (using a PC with
OE5) from another of my mail accounts to the target mailbox, both
plain text and HTML (the text portion). I can view JPG and BMP
picture attachments. URLs are also recognised (the soft key
shows "GoTo"). Having received a number of HTML messages from
others, I find I can only read the headers - even the plain text
portion doesn't show. From the size of the download, I believe
the entire message is being received (not just the header).

Does anyone have any ideas how I can read messages from people
other than myself! Could the problem be something to do with
MIME formats?