Before deploying your new mail server on the internet, make sure you have checked the list below. This will ensure that your mail server will have a good sending reputation (trusted) and will not be ignored and treated as a spammer.
Your IP addresses are not blacklisted
Even a newly setup mail server could already be blacklisted. Some of the reasons are:
- For those using a dedicated server, the IP address given to you might have been used by a spammer in the past
- For those using a shared server, a fellow user might have sent a spam mail.
- For those using NAT to share internet connection, one of your users might have sent a spam mail due to virus infection
To check if your IP address is blacklisted, use
Your mail server has an MX record
An MX record or Mail exchanger record is a type of record in the Domain Name System (DNS) specifying how Internet e-mail should be routed using the Simple Mail Transfer Protocol (SMTP). Contact your DNS provider to add an MX record for your new mail server. To check if your mail server has an MX record, use http://www.dnscolos.com.
Your mail server greeting matches your hostname
To test your mail server greeting, use http://www.dnscolos.com. If your mail server has multiple IP addresses, see Postfix Multiple IP Addresses Individual SMTP Greeting for a guide on how to fix this issue.
Your mail server is not open relay
An open relay mail server allows anyone to send mail outside your network. This means any Tom, Dick and Harry can use your mail server to send spam. To perform an open relay test, use http://www.dnscolos.com. If it fails, double check your Postfix Dovecot SASL configuration.
Your mail server has a reverse DNS
A reverse DNS returns the hostname given the IP address. Most mail servers will check if you have a valid reverse DNS, otherwise your sending reputation will be downgraded. Contact your internet service provider to add reverse DNS entries for your mail server IP addresses. To check if your mail server has a reverse DNS, use http://www.dnscolos.com.
Create a SPF DNS record if possible
Sender Policy Framework (SPF) allows software to identify messages that are or are not authorized to use the domain name based on information published in a sender policy of the domain owner. Not all DNS provider supports SPF so choosing a DNS provider that can do this is a plus. To check if your mail server has an SPF record, use http://www.dnscolos.com.
Visit the forum to ask for help or to give a comment.
Posted on 10/5/2008 and last updated on 11/6/2009
Filed under Technical Articles