When web hosting clients cannot receive email from a specific sender, they frantically call us up to know what the issue is. More than 90% of the time, the sender’s domain or email address or IP Address is blacklisted as a known spam source and is blocked by the mail server, to prevent them from sending mails. The issue lies with the senders email account, which may include issues with the domain name, DNS, IP Address or even content of the email. This article aims to educate email senders on why their mails are bouncing due to the blacklisting and how to resolve the issue to resume normal mail sending after being blacklisted.
If the web hosts mail server is an open relay server i.e. it allows any person to send out a mail without checking if he is a legitimate user or not, then such an email server is quickly exploited and gets blacklisted as a result. Novice hosting providers who are ignorant about their mail server configuration, can often cause all the clients on their machine to get blacklisted, because they may be consciously or unknowingly allowing people to use their mail server unchecked. Spammers are always on the look out for such open relay servers and grab the opportunity to pump out thousands of spam mails through such servers. The web host must deal with this by ensuring proper authentication before allowing people to relay mail from their server and also ensure proper security measures so that spam or junk mail doesn’t go unchecked.
The most common reason for an IP address getting blacklisted is having bad neighbors sharing the same IP Address. In a shared hosting environment, people share the same IP Address to send and receive mails. Any one person abusing or misusing the email service could land up getting everyone blacklisted for spamming. RBL’s or real time blacklists usually list IP addresses which are a known spam source. If you are hosted on the same IP Address as a spammer, your email service will also be affected. It’s exactly how when you roam around with criminals you may also be caught in the line of fire. If your host is continuously having IP Blacklisting issues, you may want to switch to a different host who has a better IP reputation. It simply means that the web host is unwilling or unable to contain the problematic user or stop spam from going out from the server.
Another common reason for spam mail being pumped out of your account is having vulnerabilities in your website pages. The contact form of a website is most vulnerable to hacking, as spammer try and exploit weak code to send spam mail through the form. The contact form is also the least looked after page on a website. Most coders just copy paste a template script or a ready made contact form on the website. Little do they realize that doing so may replicate those vulnerabilities again. Since contact forms already contain mail authentication information and are designed for sending out mail, malicious visitors are always on the lookout for exploiting these forms for nefarious purposes.
After putting the blame on all the above circumstances, it is a good idea to do some introspection. A common reason for blacklisting is sending out too many marketing emails, which were unsolicited, using suspicious text in your email and also using your domain name for supporting spam or any other type of illegal or malicious online activity.
You need to first check whether your domain or email account or IP address has been blacklisted. You can check this information from various online websites. After confirming that you were blacklisted, you need to determine the reason. You may want to contact your web host or ISP to determine if there is something that you can do to remedy the situation. After this, you need to do a thorough check and patch whatever vulnerabilities or exploits got you blacklisted. Sometimes things may be beyond your control, for which you may need to approach your hosting provider to help you sort out the issue.