How to avoid blacklisting your own server
There are tons of blacklists available today and, in general, blacklisting is a great way to help control the transmission of spam. For those unfamiliar with blacklisting, it is a means of blocking unwanted email by performing a lookup on the reputation of the server (IP) used to send the email. Each time an email is received, a blacklist lookup is first performed on the IP address of the server used to send the email. If the IP address comes back clean, the email is accepted. If the IP is known to be a source of Spam, the email is rejected. Simple and often effective.
Blacklisting is great for blocking spam, but it also has it's drawbacks. Particularly when you're sharing an IP address with other websites, you may find yourself in a situation where your IP is blacklisted because of the sending habits of other users. If you've ever been on a blacklisted IP yourself, you know how much of an inconvenience this can be. When your IP is on a blacklist, anyone using blacklist filtering will reject email from you!
But did you know that you, personally, could be the direct cause of blacklisting yourself!
It's true. And most people don't even realize they are doing it.
3rd party email providers like Hotmail, Gmail, AOL, etc. use blacklisting to reject email and they rely on feedback from users to identify what is spam and what is not. When you login to these email providers and check your mail, there is often a "This is Spam" button you can click to signify a given email is spam. When you click this button, these providers analyze the message headers and report the IP it originated from as a spam source. With enough complaints, this IP address may end up on a blacklist so that mail from this IP can be rejected upon receipt.
Now, let's setup an example. You just purchased hosting through Acenet and have your website online, example.com in this example. You want people to send you email at your new domain, perhaps at the email address email@example.com, but you don't want to have to check yet another email address. So instead of setting up an email account for firstname.lastname@example.org, you decide to setup a forwarder to your Hotmail account. Now, all email that is sent to email@example.com is forwarded directly to your Hotmail account. Convenient, right?
But now, ALL mail is forwarded to Hotmail. Not just legitimate mail, but spam as well. You login to your inbox at Hotmail and see all of the spam that was received at firstname.lastname@example.org and forwarded from our server. In an effort to stop these spam emails, you click "This is Spam" for each message.
And you inadvertently tell Hotmail that your account with Acenet is a source of spam!
Hotmail does not distinguish between the originating IP address and an IP address that forwarded the email. In the eyes of Hotmail, any IP that aides in the transmission of spam is considered a spam source. So by allowing spam to be forwarded from your account to Hotmail and then flagging them as spam, you can actually cause Hotmail to blacklist your server's IP address. Once this happens, all mail sent from your server's IP will be rejected by Hotmail.
We do not recommend setting up forwarders from your account with Acenet to 3rd party email services for this very reason. If you must forward mail from Acenet to 3rd party mail providers, do not click "This is Spam" for these emails.