/etc/postfix/main.cf:
smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
# Postfix 2.5 and later
smtp_tls_fingerprint_digest = md5
/etc/postfix/tls_policy:
example.edu none
example.mil may
example.gov encrypt protocols=SSLv3:TLSv1 ciphers=high
example.com verify
match=hostname:dot-nexthop protocols=SSLv3:TLSv1 ciphers=high
example.net secure
.example.net secure match=.example.net:example.net
[mail.example.org]:587 secure match=nexthop
# Postfix 2.5 and later
[thumb.example.org] fingerprint
match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
# Postfix 2.6 and later
example.info may protocols=!SSLv2 ciphers=medium exclude=3DES