[SideshowBob]

It works for me with an email client, I just sent an email with a made-up domain through mail.messagingengine.com using claws-mail. An alternative is to set up a temporary indentity in webmail.

BTW a .eml file isn't specifically a UNIX text file, it's a raw email in a native text file (i.e. a text file with native line terminators). I think the three letter file-name extention is actually from Microsoft. Strictly specking it isn't guaranteed to be text file since mime sections can contain non-encoded binaries.