spurious "from" - whose bug is it?

I have mail in my inbox from "appearances," dated "they have a wide"  :-)
(actually a continuation of the message before).  Is this a bug of Solaris,
sendmail, procmail, mailtool, or ???

First three lines of message "header":

> From appearances, they have a WIDE range of IP addresses in their DNS - I
suspect they register iki subdomains for members, and set up MX for those
users (was this mentioned?) - if you spoke nicely with your CURRENT mail