Why was there a sudden increase in Spamhaus CSS listings?
Summary
What email marketers say11Marketer opinions
Email marketer from Spamhaus Forum suggests that a sudden increase in Spamhaus CSS listings could be due to a new spam campaign or an increase in spam activity from a particular network.
Email marketer from StackExchange shares that a sudden increase in CSS listings may indicate a compromised email server or a misconfigured mail server, leading to increased spam output. Security audits should be performed.
Email marketer from Email Geeks shares a link indicating that the Spamhaus listings appeared to be a mistake and that Mailgun is re-sending impacted messages.
Email marketer from Email Geeks indicates an increase in CSS listings with Spamhaus involving random IPs across different subnets.
Email marketer from Email Geeks shares that an ESPC call mentioned a few ESPs experiencing listbomb listings.
Email marketer from Reddit r/emailmarketing suggests that compromised accounts or a sudden influx of spam reports are potential causes for a surge in Spamhaus CSS listings.
Email marketer from MailBlog suggests that you consider the idea of an outside attacker, or if there's been an inside security risk that can explain sudden spikes in blacklists. Implement security.
Email marketer from Email Geeks confirms that the Spamhaus listings were a mistake and that action was taken to reduce the impact after review.
Email marketer from EmailGeeks forum suggests a recent vulnerability or exploit in email sending software could cause a surge in spam activity, resulting in a sudden increase in Spamhaus CSS listings. Update all software.
Email marketer from MarketingPro talks about the importance of closely monitoring IP and domain reputation. A sudden increase in Spamhaus listings is an indication that action is required immediately to stop the bleeding.
Email marketer from Email Deliverability Blog explains that sudden increases in Spamhaus listings can be attributed to a variety of factors, including compromised sending infrastructure, a sudden spike in spam complaints, or aggressive spam campaigns targeting a specific IP range.
What the experts say2Expert opinions
Expert from Word to the Wise explains that a sudden increase in Spamhaus listings can significantly impact email deliverability. This expert site suggests monitoring deliverability closely and working to get delisted quickly.
Expert from Spamresource.com suggests a sudden spike in Spamhaus CSS listings may be due to an increase in spam complaints, potentially triggered by a recent campaign or change in sending practices. They recommend investigating recent email activity and feedback loops.
What the documentation says4Technical articles
Documentation from MultiRBL indicates that listings, especially on Spamhaus, are designed to stop spam. A sudden increase indicates a larger volume of unsolicited email.
Documentation from Spamhaus explains that the CSS (Composite Spam Score) list is a real-time database of IP addresses that have been detected sending spam. A sudden increase in listings suggests a higher volume of spam being sent from those IPs, triggering the listings.
Documentation from MailChannels shares that a sudden increase can be caused by new botnet activity, or a large increase in compromised email accounts being used to send spam. It is important to review sending practices and security to identify the source.
Documentation from Spamhaus FAQ explains that CSS listings are automatically removed after a period of inactivity, indicating that the spam source is no longer active. A sudden increase followed by a decrease often indicates a temporary spike in spam activity.