Ok I need some help from you technical guys out there. When I download my tracks from my Garmin to Mapsource it saves them as gdp files. That's all good. When I open it and resave it as a gpx file, that works fine too. When I try to attach it to an email and send the gpx file to someone to upload onto the challenge site, the file sends off fine from my end but never makes it to the person I'm sending it to. Any ideas on what I can do?
Try zipping the file before making it an attachment.
I have people send me files that ended up being displayed in the body of the letter as text, which made it very hard to deal with! :-)
Also, have you tried downloading the file via G7towin, GPS-Results, RealSpeed, GPS-Babel, or GPSAR or (Get My Tracks if you use a Mac). All of these utilities will produce a good file in .GPX if that is the issue.
I might actually try downloading direct to realspeed and see how that goes. Thanks for your help 
When you convert the file to GPX and save it, are you saving it to the physical hard disk? If so, then it doesnt matter how you download it, a file on the hard disk is just a bunch on zeroes and ones. Email does not discriminate.
Firewalls do though. Try emailing the .gpx file to a hotmail account and see if it arrives there.
Is the attachment visible in your sent items? Does your email have a max file size limitation for sending.
If the attachment arrives at a hotmail account, you can be sure the issue is at the receivers end. They may have a max file size limitation?
JB
