Perhaps, it very well could have been. I made an assumption since sendmail was, for the most part, the MTA in those days. Yes, others (including qmail) existed

Perhaps, it very well could have been. I made an assumption since sendmail was, for the most part, the MTA in those days. Yes, others (including qmail) existed but sendmail was, by far, the most widely used. I, myself, was a sendmail fanboy for years until I eventually moved to postfix in the early/mid-2000s.