This is what I did..

sudo apt-get install postfix

This is my /etc/postfix/main.cf:

# See /usr/share/postfix/main.cf.dist for a commented, more complete version


# Debian specific:  Specifying a file name will cause the first
# line of that file to be used as the name.  The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no


# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=no
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

myhostname = tsXXX561.server.topcloud.it

alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases

myorigin = /etc/mailname
mydestination =
relayhost = [smtp.gmail.com]:587
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = loopback-only
default_transport = smtp
relay_transport = smtp
inet_protocols = all

# SASL Settings
smtp_use_tls=yes
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_sasl_tls_security_options = noanonymous
smtp_tls_CAfile = /etc/postfix/cacert.pem

Then I created the file /etc/mailname with my hostname as content:

tsXXX561.server.topcloud.it

Then I created the file /etc/postfix/sasl_passwd:

[smtp.gmail.com]:587 [email protected]:gmail_password

Then sudo postmap /etc/postfix/sasl/passwd

sudo cat /etc/ssl/certs/Thawte_Premium_Server_CA.pem | sudo tee -a /etc/postfix/cacert.pem

service postfix restart

Still sends nothing... I'm on Ubuntu Server 12.04.