Most likely due to having your default message format set to Microsoft
Outlook Rich Text. This message format can ONLY be understood by Outlook;
everything else, Netscape, Eudora, Outlook Express, ect. will either get a
message with an attachment named "Winmail.dat" which can't be opened, or
they'll get no attachment at all. To correct this, set your default message
format to either HTML or Plain Text. Here are more words on the subject:

http://support.microsoft.com/?kbid=287720
OL2002: Attachments Are Not Visible to Some Recipients When You Use TNEF
http://support.microsoft.com/?kbid=290809
OL2002: How Message Formats Affect Internet Mail
http://support.microsoft.com/?kbid=197064
OL2000: (CW) Winmail.dat Attachments Included in Received Messages
http://support.microsoft.com/?kbid=224817
OL2000: Transport Neutral Encapsulation Format (TNEF) Basics

Decoder programs to read a WINMAIL.DAT file are he

http://www.slipstick.com/addins/decoders.htm
Decoder Tools

Hal
--
Hal Hostetler, CPBE --
Senior Engineer/MIS -- MS MVP-Print/Imaging -- WA7BGX
http://www.kvoa.com -- "When News breaks, we fix it!"
KVOA Television, Tucson, AZ. NBC Channel 4
Still Cadillacin' - www.badnewsbluesband.com

"birddog5349" wrote in message
...
I want to send my Acad .dwg files by email but Outlook keeps changing the
file to a .dat file for the recpient. How do I correct this?