/etc/postfix/main.cf

I can send and receive mail using user@example.com, but system generated emails such as root@mail.example.com bounce backup with an error:

May 1 03:14:52 mail postfix/smtp[62798]: 23CA4BD6B40: to=, relay=none, delay=0.01, delays=0/0/0/0, dsn=5.4.6, status=bounced (mail for mail.example.com loops back to myself)

How do I fix this error?

{ 5 comments }

According to RFC2821 the lowest-numbered records are the most preferred MX for domain. So I’ve a target Postfix backup server to keep the messages in a queue waiting for the primary server to become available. This ensures that if my primary MX goes down I do not loss any emails. However, spammers are connecting to my backup MX to avoid anti spam filters that are running on the primary MX server. This also hides their real IP from my primary MX. How do I configure anti-spam for my backup RHEL / CentOS 5.3 based Postfix mx server?

{ 14 comments }

How do I support multiple ISP accounts in the Postfix SMTP client (smarthost) for relaying email? For example:

[a] user1@isp1.com must be relay via smtp.isp1.com.
[b] user1@isp2.com must be relay via smtp.isp2.com.
[c] me@mycorp.com must relay all my default email via smtp.mycorp.com.

{ 6 comments }

My ISP requires that mail from my dynamic IP to our small business email addresses uses their outgoing SMTP servers. This is probably done to reduce abuse and spam but now I’m not able to send email and local Postfix log file displays authentication failure message. How do I relay mail through my mail ISP servers using Postfix SMTP under Linux / UNIX like operating systems?

{ 25 comments }

How do I bind Postfix MTA to specific IP address such as 127.0.0.1 or 202.5.1.2?

{ 2 comments }