Setup your own email server (MTA) on the cheap - part 5
Our PostFix based MTA has been running well now, and all these last changes are just securing the server from SPAM and Viruses. Traditionally SPF was a great protection from SPAM which works by comparing the server sending the message to a DNS record to confirm the validity of the sending server. A great system but it's far from perfect, and most implementations could be generously described as half arsed. To improve on SPF DKIM has been developed which uses keys to sign sent messages, then the receiving server can pull a DNS record to confirm the validity of the mail it's receiving. To do this we're going to install and use opendkim. 1. Install opendkim, of course: sudo apt-get install opendkim opendkim-tools 2. Open /etc/opendkim.conf in your favourite editor and set these four lines: Domain mydomain.com KeyFile /e...