How to identify which spam filter a company uses without directly asking them?
Summary
What email marketers say10Marketer opinions
Email marketer from SendPulse shares that using seed lists (sending emails to a list of test accounts with different email providers) can help identify if specific spam filters are blocking emails. By analyzing which seed accounts receive or block the emails you can get an indication of the spam filter used.
Email marketer from Mailjet explains that analyzing bounce codes can provide clues about why emails are being blocked, potentially indicating which spam filter is in use. Specifically look for codes relating to content or reputation rejections.
Email marketer from Neil Patel's Blog suggests using tools to check your sender reputation, as many spam filters block emails from senders with poor reputations.
Email marketer from Reddit user u/EmailExpert shares checking common email blacklists to see if your sending IP or domain has been listed. If you find yourself on specific blacklists (like Spamhaus or Barracuda), it may indicate the filtering service the recipient is using.
Marketer from Email Geeks explains that it becomes more challenging if it's connected to O365 via a connector, where O365 accepts the email and then passes it to a third-party filter before acting. Recommends first checking the MX records.
Email marketer from Litmus shares advice on performing inbox placement tests to identify if emails are landing in the inbox, spam folder, or being blocked. Analyzing the results can help pinpoint which email providers are filtering your emails.
Email marketer from StackExchange explains to check SPF, DKIM, and DMARC records. Incorrectly configured records can cause emails to fail authentication checks, which might get flagged by spam filters.
Email marketer from Gmass suggests gradually increasing your sending volume to build a positive sending reputation. A sudden spike in email volume can trigger spam filters.
Email marketer from Email Marketing Forum user SpamSlayer suggests analyzing your email content for commonly flagged keywords or phrases often associated with spam. Modify your content and resend test emails to see if the issue persists.
Marketer from Email Geeks suggests checking the MX records using a DNS query tool. Then Google what it resolves to, to see if it's a filtering service like Proofpoint, Mimecast, or Barracuda.
What the experts say2Expert opinions
Expert from Word to the Wise, Laura Atkins, explains that one indirect method is to analyze the headers of bounced emails. Look for clues such as 'X- एंटी-spam' or similar headers that indicate the presence and type of anti-spam system being used.
Expert from Spam Resource explains utilizing RBL (Real-time Blackhole List) lookups and setting up feedback loops. RBLs help identify if your IP is listed due to spam activities. Feedback loops from ISPs provide data on spam complaints, helping pinpoint issues.
What the documentation says5Technical articles
Documentation from RFC 5321 explains that SMTP error codes (found in bounce messages) can provide specific details about why an email was rejected, offering insight into which spam filter's rules were triggered. Look for 5xx codes for permanent failures and examine the accompanying text.
Documentation from Barracuda explains that if you're blocked by Barracuda Reputation Block List (BRBL), it means Barracuda's systems have identified your IP as a source of spam. Check their site for removal requests.
Documentation from Microsoft Learn details how Exchange Online Protection (EOP) filters inbound emails, including spam filtering techniques. Examining message headers can reveal whether EOP flagged the email as spam, indicating its use.
Documentation from Spamhaus details their various blocklists and how to check if your IP address or domain is listed. Being on a Spamhaus blocklist means many organizations using their data feed will reject your emails.
Documentation from Cisco Talos details how their reputation services work and how to check if your IP address or domain is on their blocklists. If Talos is blocking you, the recipient organization is likely using Cisco's security products.