Using google mail servers as a smarthost from a linux server (ubuntu)

So you want to send mail securely using google's mail servers as a smarthost.

The first thing you'll need is an application specific password for exim.

Once that's created, I will assume the following:

• You are ok with Gmail rewriting your sender address or use this Gmail address.
• Your account name on your local Debian box: YOUR-USER-NAME
• Your host name in /etc/hostname: hostname1
• Your host name in the 127.0.1.1 line of /etc/hosts: hostname1.localdomain hostname1
• Your envelope address is SMTPAccountName@gmail.com for the outgoing SMTP connection to Gmail's SMTP server via Exim4
• Your Exim4 relays local SMTP connections coming with the mail envelope address: YOUR-USER-NAME@localhost and YOUR-USER-NAME@localhost.localdomain
• Your account name for SMTP at Gmail is SMTPAccountName@gmail.com
• Your password for SMTP at Gmail is y0uRpaSsw0RD
   

# dpkg-reconfigure exim4-config

• Choose "mail sent by smarthost; received via SMTP or fetchmail"
• Set to "localhost" for "System mail name:".
• Set to "127.0.0.1" for "IP-addresses to listen on for incoming SMTP connections" to refuse external connections.
• Leave as empty for "Other destinations for which mail is accepted:".
• Leave as empty for "Machines to relay mail for:".
• Set to "smtp.gmail.com::587" for "IP address or host name of the outgoing smarthost:".
• Choose "NO" for "Hide local mail name in outgoing mail?".
• Choose "NO" for "Keep number of DNS-queries minimal (Dial-on-Demand)?".
• Choose "mbox format in /var/mail/" for "Delivery method for local mail".
• Choose "YES" for "Split configuration into small files?".

vi /etc/exim4/passwd.client

add the following lines:

*.google.com:SMTPAccountName@gmail.com:y0uRpaSsw0RD

# chown root:Debian-exim /etc/exim4/passwd.client # chmod 640 /etc/exim4/passwd.client

Edit your aliases file

# newaliases

# update-exim4.conf
# invoke-rc.d exim4 restart
# exim4 -qff

 tada

mostly grepped from here 

Getting Mac OS X to use google apps as a mail proxy

First of all, I have a macbook air which mails me everytime it wakes up, it's status and it's current IP.

I had this originally use my firewall at home as a mail proxy, but obviously, when am *not* at home, this doesn't work.

So what I configured is how to use google's mail server to act as my SMTP server over SSL - great huh?

I would suggest you setup a sub domain e.g. sub.domain.com so that it was it's own set of credentials and security, and doesn't use your main account (which will have admi rights for the entire domain) e.g. I own bobcats.org, and the address phil@bobcats.org, so I'll setup root@sub.bobcats.org as the subdomain and email address for my mac's admin account.

So what do you need to do?

*/ Setup postfix
*/ setup google
*/ setup DNS
*/ setup site verification (web)
*/ setup site verification (mail)
*/ Profit

Setup postfix

You'll need to setup a Simple Authentication and Security Layer (SASL)

vi /etc/postfix/sasl_passwd

with the following:

smtp.gmail.com:587 your.name@gmail.com:your.password

Create a postfix lookup table for SASL:

postmap /etc/postfix/sasl_passwd

Configure postfix with:

vi /etc/postfix/main.cf

with the following:

# Minimum Postfix-specific configurations.
mydomain_fallback = localhost
mail_owner = _postfix
setgid_group = _postdrop
relayhost=smtp.gmail.com:587
# Enable SASL authentication in the Postfix SMTP client.
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options=

# Enable Transport Layer Security (TLS), i.e. SSL.
smtp_use_tls=yes
smtp_tls_security_level=encrypt
tls_random_source=dev:/dev/urandom

Setup google

This will involve going into your dashboard - just google "google apps"
add your (sub) domain into the domain tab of settings.

Setup DNS

Point DNS to a webserver that you own 

Setup site verification (web)

This will involve placing a specially crafted text file (supplied by google) onto that site

Setup site verification (mail)

This will involve adding a TXT record for the above (sub)domain

Profit