See if anything here helps:

Outlook Express message appears blank and has an ATT000XX.txt or an
ATT000XX.htm attachment:
http://support.microsoft.com/?kbid=312351

And from:
http://pages.prodigy.net/michael_santovec/decode.htm

Besides the problem described in this article with temporary files, Outlook
Express may have a blank message if Internet Explorer is set at View,
Encoding to Auto-Select. If so, disable the Auto-Select in Internet Explorer
and choose instead Western European (ISO). If your program has an option to
read HTML messages in Plain Text, the HTML version of the message may appear
as an ATT0001.HTM attachment (the number may vary).

For the *access* question:

ToolsOptionsSecurity. Uncheck: "Do not allow attachments................."

Help avoid computer viruses that spread through e-mail
Managing e-mail attachments in Outlook and Outlook Express
http://www.microsoft.com/athome/secu...tachments.mspx

If you're running XP/SP2 also see this:
Description of how the Attachment Manager works in Windows XP Service Pack
2:
http://support.microsoft.com/?kbid=883260

And please see these articles about virus protection in OE 6:

http://support.microsoft.com/?kbid=291387
http://support.microsoft.com/?kbid=329570
http://insideoe.tomsterdam.com/faqs/why.htm#oe6attach
--
Bruce Hagen
MS-MVP Outlook Express
~IB-CA~

"HarryS" wrote in message
...
What are the email attachments of the type 'ATT00026.xxx' that I receive
with many emails. I've seen these attachments every so often, usually
when there is also an attached .gif or .jpg file. I also started getting
a pop-up message when I send and email that says "OE removed access to
the following unsafe attachments in your mail: ATT00090.htm".

Even if I can't eliminate the ATT attachments on received emails, I'd like
to stop the pop-up messages.

Thanks for any help you can give on this.

HarryS