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Resolving: This message was classified as rSPAM and may not be delivered

If you recently received a bounce-back message stating, “This message was classified as rSPAM and may not be delivered,” your email was blocked at the SMTP level before leaving our servers. This preventative block triggers for several reasons, ranging from missing Sender Policy Framework (SPF) records on your domain to a potential security compromise.

When an email is blocked, your bounce message will include a URL starting with mail.outboundspamprotection.com. You can visit this link to see exactly which spam rules your message triggered, and you will also have the option to mark the email as “not spam” if it was flagged in error.

Understanding Your Specific Error Code

Look closely at your bounce message. Following the standard “550” error, you will see an additional three-digit code that pinpoints the exact cause of the block.

Code 100: Compromised Account or Local Blacklist

  • The Issue: Security lockdown. This triggers when rules (such as COMPROMISED_EMAIL_FROM_BLACKLIST or LOCAL_BL_FROM) detect unauthorized traffic or a manual blacklist flag. A common cause is an exposed password—often left in a publicly accessible .env file inside a PHP script that should have been kept outside the document root.
  • What It Means For You: Your sending mailbox or web system has likely been compromised by a spammer. You must secure your account immediately, update your email passwords, and audit your files for vulnerabilities. A manual delist is needed, please use the not spam report in this case or reach out to support.

Code 200: SPF Authentication Failure

  • The Issue: Domain misalignment. This code groups together rules like SENDER_FAILS_SPF_SPOOF and REDIS_SPFFAIL_CHECK.
  • What It Means For You: Your domain’s DNS settings do not authorize MailBaby to send mail on your behalf. To fix this, update your domain’s external SPF record to include MailBaby so your messages pass standard anti-spoofing checks. Fixing spf will automatically fix this error generally with in an hour, or reach out to support to manually retest.

Code 300: Malware and Virus Hits

  • The Issue: Dangerous attachments. This code is triggered by our backend scanners hitting rules like CLAM_VIRUS or DBL_MALWARE.
  • What It Means For You: The email contains a file attachment flagged as malicious. The message cannot be sent as-is. Delete the attachment, and run a thorough malware scan on the device you are sending from. No manual intervention is needed in this case as the email is not locked however reach out to support with questions as to why a listing may exist.

Code 400: Content Filtering & Fuzzy Matches

  • The Issue: Text and layout triggers. This code groups rules like FBL_FUZZY_DENIED and FUZZY_PLUS_DENIED.
  • What It Means For You: The body text, HTML structure, or links inside your email too closely resemble known, repeating spam campaigns. Tweaking your wording, removing suspicious links, or simplifying your formatting will usually get the message through. No manual intervention is needed in this case as the email is not locked however reach out to support with questions as to why a listing may exist.