More to that: I want to add an IP range to whitelist and enable SMTP Auth Bypass. After I enable the setting, it reverts back to OFF. All other settings (SMTP, POP, IMAP, XMPP) remains ON, but SMTP auth Bypass changes back to OFF.
It seems we can't change anything related to SMTP protocol.
Please help, this is very annoying. Before upgrading to SM 16.3 from 15.7 we did not had this problems.