You can use sasldb2 for authentication, to add users use:

	saslpasswd2 -c username

If you want to enable SMTP AUTH with the system Sendmail, read
Sendmail.README

NOTE: This port has been compiled with a default pwcheck_method of
      auxprop.  If you want to authenticate your user by /etc/passwd,
      PAM or LDAP, install ports/security/cyrus-sasl2-saslauthd and
      set sasl_pwcheck_method to saslauthd after installing the
      Cyrus-IMAPd 2.X port.  You should also check the
      %%PREFIX%%/lib/sasl2/*.conf files for the correct
      pwcheck_method.
      If you want to use GSSAPI mechanism, install
      ports/security/cyrus-sasl2-gssapi.
      If you want to use SRP mechanism, install
      ports/security/cyrus-sasl2-srp.
      If you want to use LDAP auxprop plugin, install
      ports/security/cyrus-sasl2-ldapdb.