Don't get me wrong: I'm not defending faxes. The level of investment in actual paper in the legal and medical professions, though, should never be underestimated.

There's absolutely no good reason to trust a FAX machine's ability to confirm receipt any better than a mail server's.

And here the key difference between email and fax rises to the surface: the email only exists on paper after it is printed, and many aspects normal to emails (sound, animation) won't print.

One tech embraces print; the other does not. When a doc has to sit in a file box for decades without significant degradation, that must be considered.