bsd-mailx binary package in Ubuntu Xenial amd64

 bsd-mailx is the traditional simple command-line-mode mail user agent.
 Even if you don't use it, it may be required by other programs.
 .
 The /usr/bin/mail command provided by this package is a very simple one,
 and does not include many features that can be found in more advanced
 mail user agents.
 .
 For example bsd-mailx DOES NOT support:
  - MIME (i.e. no attachments, no UTF-8 or other charsets support);
  - SMTP protocol (/usr/sbin/sendmail interface only is used);
  - POP3/IMAP (bsd-mailx reads local mailboxes only);
  - maildir format (traditional mbox only format is supported).
 .
 If the above features are needed, please consider installing another package
 providing similar /usr/bin/mail interface:
  - heirloom-mailx package,
  - or mailutils package.

Source package