What common blocklists or services cause 'message rejected as spam' errors for ESPs?
Summary
What email marketers say10Marketer opinions
Email marketer from Email on Acid recommends monitoring your sender reputation using tools like Google Postmaster Tools and Microsoft SNDS. These tools provide insights into your IP and domain reputation and can help you identify and address deliverability issues.
Email marketer from Email Marketing Forum mentions URIBL (Uniform Resource Identifier Block List) as a common blocklist. They explain that URIBL lists domains found in spam emails, so ensuring your links are clean is crucial.
Email marketer from Mailgun explains common reasons for blocklisting, including high spam complaint rates, sending to invalid email addresses (high bounce rates), and failing to authenticate email with SPF, DKIM, and DMARC.
Email marketer from Reddit explains that being listed on Spamhaus can cause major deliverability issues. They recommend checking their website and following their delisting procedures if you are listed.
Email marketer from Quora highlights that ESPs can be blocklisted if their users send spam. Monitoring user behavior and enforcing strict anti-spam policies is essential.
Email marketer from Talos Intelligence explain that they offer sender reputation services, providing valuable insights into the standing of your email infrastructure. This helps identify and address potential deliverability issues promptly.
Email marketer from Email Geeks shares a link to a tool to check for false positives: <https://sendertool.vadesecure.com/en/>
Email marketer from Litmus advises to maintain good email hygiene practices, such as regularly cleaning your email list to remove inactive or invalid addresses, segmenting your audience to send more targeted emails, and actively monitoring your sender reputation.
Email marketer from SendGrid shares that tools like MXToolbox and GlockApps can be used to check if your IP address or domain is listed on various blocklists. These tools scan multiple blocklists simultaneously and provide a comprehensive report.
Email marketer from StackOverflow explains that Dynamic IP blacklists, like those from Spamhaus (ZEN), are used to block IP addresses that are typically assigned to dial-up or residential internet connections. Sending email from these IPs is often considered suspicious.
What the experts say5Expert opinions
Expert from Word to the Wise shares that SenderBase (now part of Cisco Talos) provides reputation scoring based on email traffic and other factors. A low SenderBase reputation can impact deliverability and potentially lead to message rejections.
Expert from Email Geeks suggests that multiple ISPs may be using Vade Retro.
Expert from Email Geeks mentions that the rejection message sounds like it's content or fingerprint based. The expert then suggests checking the links in the message as well as the sending IPs, and shared click or open trackers.
Expert from Word to the Wise explains that the Return Path Reputation Blocklist (now Validity) is a common blocklist used by many ISPs and email filtering services to identify and block senders with poor reputation.
Expert from Spam Resource emphasizes the importance of having valid PTR records (reverse DNS) that match your sending IP addresses to your domain. Lack of proper PTR records can lead to deliverability issues and being blocklisted.
What the documentation says5Technical articles
Documentation from Google details their bulk sender guidelines, which include authenticating email with SPF, DKIM, and DMARC; keeping spam rates low; and providing easy unsubscribe options. Failure to comply can lead to deliverability issues.
Documentation from Proofpoint explains that they use a reputation system to analyze email traffic and identify spam sources. Their blocklists are dynamic and based on various factors, including message content, sending behavior, and IP reputation.
Documentation from Spamhaus explains that the Spamhaus Block List (SBL) is a real-time database of IP addresses involved in spamming and other malicious activities. Being listed on SBL can cause email rejections.
Documentation from BarracudaCentral shares that their reputation blocklist is based on real-time analysis of email traffic across their network. Listing usually occurs due to poor sending practices, spam content, or compromised accounts.
Documentation from Microsoft shares that Outlook.com uses a complex sender reputation system. Factors include spam complaint rates, bounce rates, and user engagement. Low sender reputation can result in messages being rejected or sent to the junk folder.