It is always mandatory to create a backup before making any changes to any server. If you do not have a backup: Purchase the IONOS Cloud Backup, follow the installation instructions, and complete a manual backup (video).
Operating a mail server without learning best practices is like operating a motor vehicle without obtaining a license.
Chances are that you’ve stumbled on a ‘UCEPROTECT’ blacklisting of your server from mxtoolbox.com. Although you may (or may not) be having email sending issues, I’d like to start by pointing out: UCEPROTECT L3 listing is NOT the reason, UCEPROTECT L1/L2 listing may be the reason, and neither are the cause. The
problem is your server, your DNS, your content, or every so often–your neighbors.
UCEPROTECT is not the problem
UCEPROTECT has every IP address of many major web hosting and server providers included in their Level 3 (L3) listing. This is because most web hosting companies allow customers to set up and run their own mail servers without proof of being a certified admin or having one on call. However, being a Mail Server Admin requires sound knowledge of administrating such systems. Web hosting companies also allow customers to freely change their server’s IP address, which can be used as a sneaky way to circumvent spam filters. Furthermore, UCEPROTECT is one of the most aggressive mail filters on the net, and one of their requirements is having two IP addresses for every mail server: one for sending clean emails, and one for internally marked as spam. As you may know, most web hosting companies don’t requirement their customers to adhere to this.
With all of this said, however, no major email providers that base their email blacklisting or spam filter on the L3 listing, and UCEPROTECT advises against any mail providers from doing such:
“NOTE: By using Level 3 for blocking, be prepared to occasionally lose some required mails too. DO NOT BLAME US, YOU HAVE BEEN FOREWARNED!”https://www.uceprotect.net/en/index.php?m=3&s=5
Instead, email providers will use the L1 or L2 listing. L1 blacklisting is specific to only your server’s IP. L2 happens when a certain number of servers within the same web hosting network are L1 listed at once. L2 listing is also dependent on how many IPs your provider owns, how they allocate them to customers, and how abusive your neighboring customers are with their mail servers.
Solving email deliverability issues
If you are having actual email sending issues, it’s better to investigate the root cause.
First, you can actually query your server with UCEPROTECT themselves. This is done here:
After entering the IP address of your server you can see if it is listed in L1 or L2. This page is also useful because it will point out rDNS issues as well, which will be seen as:
"WARNING: No Reverse-DNS (PTR) is assigned to your IP"
Other things to look for:
- Does your domain have a valid SPF record?
- Does your domain have a valid DMARC or DKIM record?
- Does your email client have valid server settings (hostname, port, credentials)?
- Does your email server require authentication?
- Does your email server have an effective internal spam filter?
- Does your email server have two IP addresses for sending clean vs filtered email?
- Are all website contact forms that send out emails protected against vulnerabilities and using Captcha?
If you answered no to any of the questions above and sent even one email from your server/domain within the last 7 days, this is enough reason to be caught on a blacklist, or for your emails to be delivered into Spam. To resolve your email sending issues, fix all of the issues above, and wait for your server to be automatically delisted.