Setting up Postfix for sending mail
12 August 2017
Credit to others
The work in here was really done by other people. In particular, one guide that really helped me was from Ben von der Weiden with his guide on setting up smartmontools. During this guide, Ben talked about how to set up Postfix so that you can receive external mails with updates on errors.
For the most part I’m just going to quote Ben, as he’s already said what needs to be said. I’ve edited some steps in the process, though.
Setup
The very first thing to do is sign up for a free email account just to be used for this computer. I’m going to refer to this email address as server-email@provider.com throughout. If I refer to your-email@address.com then that’s, well, your normal email address.
One final point, because there’s a mixture of text to input into files and command line input, you should be aware that where the usual shell commands (e.g. sudo vi /etc/file) you don’t put that into the file but you enter it to the shell after adding the previous command. Having said that, I’ve tried to split the file input away from the shell commands.
Open your shell programme, then we’ll move to the directory and copy the original file, so that we have our vanilla settings available:
$ cd /etc/postfix
$ sudo cp -i -p main.cf main.cf.default.orig
$ sudo vi /etc/postfix/main.cf
First check out the IMAP settings for your host then add the following lines below the commented out relayhosts, replacing the part in square brackets if it’s different for your provider:
relayhost = [smtp.provider.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_use_tls = yes
Find the section below about address rewriting (otherwise GMX will reject the emails as ‘unauthorised sender’) then add the following uncommented lines below:
# ADDRESS REWRITING
#
# The ADDRESS_REWRITING_README document gives information about
# address masquerading or other forms of address rewriting including
# username->Firstname.Lastname mapping.
sender_canonical_maps = pcre:/etc/postfix/canonical_sender
recipient_canonical_maps = pcre:/etc/postfix/canonical_recipient
Now we’ll edit the postfix settings, some of this is on the usual Postfix setup guides, but the part about setting up the canonical_sender and recipient that we just started that I found to be really important:
$ sudo vi /etc/postfix/sasl_passwd
add the following line:
[smtp.provider.com]:587 server-email@provider.com:password
$ sudo chmod 600 /etc/postfix/sasl_passwd
$ sudo postmap /etc/postfix/sasl_passwd
Now for the canonical_sender:
$ sudo touch /etc/postfix/canonical_sender
$ sudo chmod 644 /etc/postfix/canonical_sender
$ sudo vi /etc/postfix/canonical_sender
add the following line, then we’re moving on to canonical_recipient:
/.+/ server-email@provider.com
$ sudo touch /etc/postfix/canonical_recipient
$ sudo chmod 644 /etc/postfix/canonical_recipient
$ sudo nano /etc/postfix/canonical_recipient
add the following line:
/.+/ your-email@address.com
$ cp -i -p /etc/aliases /etc/aliases.default
$ sudo vi /etc/aliases
Edit the following line:
# Person who should get root's mail. Don't receive mail as root!
root: your-email@address.com
below all specific aliases add this:
*: your-email@address.com
Then run a quick:
$ sudo newaliases
and send a test email:
$ date | mail -s "subject" your-email@address.com