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?
How do I support multiple ISP accounts in the Postfix SMTP client (smarthost) for relaying email? For example:
[a] email@example.com must be relay via smtp.isp1.com.
[b] firstname.lastname@example.org must be relay via smtp.isp2.com.
[c] email@example.com must relay all my default email via smtp.mycorp.com.
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?
How do I force apt-get to send me email when upgrades or security updates available under Debian or Ubuntu Linux? Do I need to write a shell script which generates a mail with a list of all packages currently pending an upgrade?
Can you explain DNS name resolution concept? Why I need to set DNS resolution for my Windows or Linux server? How do I setup DNS name resolution under Linux / UNIX server system?