configure Ubuntu to send mail (as an SMTP client using postfix)

EDIT: these instructions are pretty convoluted, I will redo them here.

    1. We will start with a trusty DigitalOcean instructional – at least step 1 of that instructional.
      sudo apt-get install mailutils
    2. I want to send mail using mailgun, which allows for ports 25, 587 and 465 (SSL/TLS). I’ll use 587 which is called submission in postfix terminology, I guess due to 587 being the proper port for TLS email submission. Because I want to use encryption (SASL) (or whatever), I need to setup Postfix accordingly. I changed my Postfix config file as such
       ubuntu@machine_name:~$ sudo nano /etc/postfix/
      #various stuff above
      relayhost = []:submission
      mynetworks = [::ffff:]/104 [::1]/128
      mailbox_size_limit = 20000000
      recipient_delimiter = +
      inet_interfaces = all
      inet_protocols = all
      smtp_sasl_auth_enable = yes
      smtp_tls_security_level = encrypt
      smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd

      Some of these settings are related to the DigitalOcean instructional, such as custom mailbox_size_limit. Make sure all the smtp settings are there

  1. Then I want to enter in my SMTP login details:
    ubuntu@machine_name:~$ sudo nano /etc/postfix/sasl_passwd

    []:submission name@domain:password

    – maintaining the important requirements shown in the link in part 2.

  2. hash the file for postfix:
    ubuntu@machine_name:~$ sudo postmap /etc/postfix/sasl_passwd
  3. change the password file permissions:
    ubuntu@machine_name:~$ sudo chmod 770 "/etc/postfix/sasl_passwd"
    The file should already have: sudo chown root:root “/etc/postfix/sasl_passwd”
  4. I changed some of the TLS settings in the config as talked about here.. (note sure of the relevance)
    # TLS parameters
  5. I went to step 3 of the DigitalOcean instructional, sent email and checked the log (at “/var/log/syslog”).. I don’t really like the email sender, despite setting myorigin (myorigin = /etc/mailname etc) and myhostname in the config, which leads to here (step 7). Although I couldn’t use echo and had to change the settings with nano.
  6. So I sent an email using step 3 of DigitalOcean instructional again, and it looks nicer (using mailgun as the MTA and MDA – since mail forwarding on my domain provider is crappy).
    One of the number of awesome things about mailgun is that I can send mail from a different sender than the one authenticating via SMTP.. a really sweet feature.
  7. As in step 5, I created: sudo nano /etc/postfix/generic
    ubuntu@hostname externalemailaddress@domain
    username@hostname  externalemailaddress@domain
    root@hostname externalemailaddress@domain
    @hostname @domain
    #use 'postmap /etc/postfix/generic' to hash this file
    #then 'service postfix restart'

    I added the second line which happily caught mail for postmaster as in step 4 of the DigitalOcean instructional.
    Add this to the config

    smtp_generic_maps = hash:/etc/postfix/generic
  8. Reading the comments in the DigitalOcean instructional it seems many are having trouble with their step 4, I fixed this by commenting out
    mydestination = localhost

    and adding simply

    #mydestination = localhost
    mydestination = localhost

    It seems the aliases settings are basically ignored since we aren’t using the local address class…

  9. restart postfix
    sudo service postfix restart

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