Smail vs. sendmail

Rick Troxel wrote,

| I use procmail a bit on a system running smail and have found its use
| the same as on this system, which runs sendmail.

One difference is that Smail couldn't care less about the value of EXITCODE.
Tricks like

    :0
    * cause to believe you should pretend to this sender that you don't exist
    { EXITCODE=67
      HOST }

work under sendmail (they send back the NDN) but not under Smail (no NDN is
returned).