The message is (a bit) suspicious because some viruses use the following trick: they've an attachment called e.g.
Info.txt .exe
Because the window in which the names are displayed has a size limitation, it's quite likely that the .exe extension will not be displayed (will be clipped), making the user think that it's a TXT file, instead of an EXEcutable.
If you want, you can turn off the whitespace checking but in 99.9% of cases you shouldn't really see any (legal) attachments with names like that...