E-Mail with attachments (3,5 MB in Entourage. Why? I just added two files as an attachment to an e-mail in MS Entourage 2004.
In Finder, the files have a size of 2,5 MB respectively 205 kB.

When I send them as an e-mail, Entourage tells me that the sent mail has a size of 3,5 MB!


Why? Does this have to do with AppleDouble encoding?
Is there a way to avoid that increase in size?
This isn't an Apple or Entourage issue, this is normal behaviour that happens when attachments are encoded to be sent with emails -- encoding the data to the email format makes the attachments roughly one-third heavier. 

This has nothing to do with the Apple filesystem. 

There is no way to stop this happening. If file size is a problem, consider uploading to an FTP server, or using a system like Box.net, YouSendIt, or DropBox to share the files -- these methods don't require encoding and will not increase the size.