[Nmh-workers] Garbage collect SENDMAILBUG code

[Ken Hornstein]

There is code in mts/smtp/smtp.c with the following comment:

#ifdef SENDMAILBUG
/*
 * It appears that some versions of Sendmail will return Code 451
 * when they don't really want to indicate a failure.
 * "Code 451 almost always means sendmail has deferred; we don't
 * really want bomb out at this point since sendmail will rectify
 * things later."  So, if you define SENDMAILBUG, Code 451 is
 * considered the same as Code 250.  Yuck!
 */
#endif

I think this is long-obsolete, and I propose we remove it.  Objections?

--Ken