Does anybody have an answer to to this? In Mail, I sometimes get phishing and spam emails. I like to save them as raw message source and then change the file extension to ".txt" to examine the content safely. When the file saves, the Finder renders an icon from the content and I'm worried that it might be connecting to external servers when it does that. I try saving the email with a .txt extension, but Mail forces it back to .eml. Is there a way to turn that behavior off?