How to get postfix working on CentOS 6 and Comcast. Recently, they've changed their policies regards email relay and require authentication even to send email. (they no longer use IP address ranges, presumably in an attempt to curb outgoing SPAM)
I didn't see an updated howto anywhere on the Interwebs, thought I'd point out what I had to do. The part that had me stumped for longer than I care to admit was having to install cyrus-sasl-plain rpm - EL5 apparently had that installed as part of the cyrus-sasl package.
1) yum install postfix cyrus-sasl-plain; # note that cyrus-sasl-plain is NOT installed by default but is needed by this config.
2) Create file /etc/postfix/passwords. Replace "USERNAME" with your user name, and "password" with your password. Note: your username is typically your email address without the domain name. #---------------------------- smtp.comcast.net:587 USERNAME:password smtp.comcast.net USERNAME@comcast.net:password #----------------------------
3) makemap passwords;
4) Edit /etc/postfix/main.cf #---------------------------- relayhost = [smtp.comcast.net]:587 smtpd_sasl_auth_enable = yes smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/passwords # note that with no security options on, we're using sasl-plain installed above. smtp_sasl_security_options = # You might need this, you may not. #sender_canonical_maps = regexp:/etc/postfix/sender_rewrite #----------------------------
5) Create file /etc/postfix/sender_rewrite. Note that not all Comcast customers need this, I didn't when I authenticated as above. Obviously, replace "USERNAME" with your user name. #---------------------------- /^([^@]*)@.*$/ USERNAME@comcast.net #----------------------------
6) service postfix stop; sleep 5; service postfix start