Postfix attempts to be fast, easy to administer, and secure, while at the
same time being sendmail compatible enough to not upset existing users.
Thus, the outside has a sendmail-ish flavor, but the inside is completely
different.

Port flavors:

ipv6	support IPv6 (${IPV6HOMEPAGE})
tls	support SMTP over SSL/TLS (${TLSHOMEPAGE})
sasl	support authenticated SMTP using Cyrus SASL v1 (deprecated)
sasl2	support authenticated SMTP using Cyrus SASL v2 (recommended)
pcre	support table lookups using PCRE (Perl-Compatible Regular Expression)
ldap	support table lookups using LDAP
mysql	support table lookups using MySQL
pgsql	support table lookups using PostgreSQL
