Hi,
I've got the same issue here.
Here are the details:
Android 8.0.0 @ Asus_Z017D (ZenFone 3), Enpass 6.0.6.200.
I've been sending the e-mail as a reply via the Gmail app. Yes, there was a signature attached but has not contained any files in it and I didn't intend on attaching an enpass file. As for now, this is the only instance of this behavior.
EDIT:
I've just checked: It happens at least since the beginning of April.
EDIT again:
It seems, that the attachments are visible with MS Outlook (I haven't got any other e-mail app, so I can't check it), and I've found them on e-mails back up to June 2017! Guys, there's something really wrong there
Cheers,
Rafał