I installed SSMTP as suggested in the handbook, but it does seem that it send Bcc: headers in clear also to the To: recipients. https://www.freebsd.org/doc/handbook/outgoing-only.html There seems to be an (inactive) bug upstream: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=492857 We might want to have a local patch or suggest a different system (Google suggests msmtp, but I didn't try that) in the handbook. Or, maybe, at least add a headsup regarding this potentially troublesome bug.
Testcase: `echo Test. | mail -s Subject -b addr1@dom addr2@dom`
Lapo, This is obviously an upstream issue. Please report it to the upstream maintainer here https://www.debian.org/Bugs/ Thank you for the report! Yuri