I got to spend some time this weekend setting up a mailserver for my personal domain (adamogrady.id.au) and thought I'd jot down some points on this blog. In particular my mail setup uses a [Postfix](http://www.postfix.org/) MTA that forward emails from all addresses to a single user, stores messages in the [Maildir](http://cr.yp.to/proto/maildir.html) format and forwards a copy of everything to my [Gmail](https://mail.google.com/) account (which I use for the web interface and which has been my primary address for some time). In particular I've done this so I can use different aliases to sign up to various services (facebook@, twitter@, etc) or give out to different people/groups to keep better track of where emails are coming from (and whose selling my details to spammers).

Firstly we should set up our DNS. Create an A record that will be the hostname of your mail server prepended to the domain such as "mail0.example.com". Next create an MX record  for your domain with a high priority (I use 10) that points to the hostname+domain combo you set just prior. Also make sure that there is a [PTR record](https://web.archive.org/web/20160508073457/https://kb.intermedia.net/Article/1317) for the IP your server uses that is set to your domain (you'll need to go to your server hosting provider for this). Probably good to set up an [SPF record](https://www.digitalocean.com/community/tutorials/how-to-use-an-spf-record-to-prevent-spoofing-improve-e-mail-reliability) in your DNS by creating a TXT record for your domain with the data being your SPF setup (I've used `v=spf1 a -all` for my domain).

To setup Postfix on Ubuntu 14.04, run `sudo apt-get install postfix` and select the option that puts you as an Internet Site and put your domain in the next requested field. Go to /etc/postfix/main.cf and make sure `myhostname` is set to the hostname+domain of the server, `myorigin` can be `/etc/mailname` as long as that file is just the domain. `mynetworks` should only have localhost entries in it (such as 127.0.0.1) to prevent it being used as an open relay and make sure the bottom three lines are as follows:

	home_mailbox = Maildir/
	mailbox_command =
	virtual_alias_maps = hash:/etc/postfix/virtual

This tells Postfix to use Maildir storage system and sets up to allow virtual aliases. Next create the /etc/postfix/virtual file and set the contents to the following:

	@[DOMAIN]       root [Gmail ADDRESS]

This sets a "catch-all" for your domain and stores messages in root/Maildir as well as forwarding a copy to the specified Gmail address. Run `postmap /etc/postfix/virtual` then `postfix reload` to load up the alias and restart Postfix.

To give ourselves some reliability we'll spin up another (smaller) server, preferably in a different location, to use as a backup store-and-forward mail server. We'll go back to whatever DNS hosting control panel we use and add a new A record for the new server and another MX record (with a lower priority) pointing to the A record. Install Postfix again, choosing the same options as last time than open your /etc/postfix/main.cf and add the following lines:

	relay_domains = example.com
	smtpd_recipient_restrictions = permit_mynetworks,reject_unauth_destination
	transport_maps = hash:/etc/postfix/transport

It's also important to make sure the domain specified in `relay_domains` is not also found in `mydestination` and if it is, remove it from `mydestination`. Then open /etc/postfix/transport and add the following

	eample.com :[mail0.example.com]

Where "mail0.example.com" is the hostname+domain or IP of your primary mail server. Run `postmap /etc/postfix/transport` then `postfix reload` on this server and it should be all configured.