(info "(mailutils) Mail Variables") says 3.5.6 How to Alter the Behavior of 'mail' -----------------------------------------
Following variables control the behavior of GNU 'mail': Mention [yes, also right on that page!] if one can use e.g., $ mail --set=sendmail=sendmail:/usr/lib/sendmail ... $ mail --set=sendmail=/usr/lib/sendmail ... $ mail --set=sendmail=/usr/lib/sendmail ... $ mail --set=sendmail=/usr/lib/sendmail ... $ mail --set=metoo=False etc. to in some fashion alter them from the command line, and why not if not.
