MailFixIt

Gmail content security rejection

Gmail 552 5.7.0: "potential security issue"

Gmail rejected something in the message or an attachment as potentially unsafe. Find and replace that content; changing SPF, DKIM, or DMARC will not fix this response.

Problem description

The Gmail response is:

552 5.7.0 This message was blocked because its content presents a potential security issue.
Is this temporary or permanent?

SMTP 552 is permanent for this message. Retrying the same content will normally fail again.

See Google’s official explanation of why Gmail blocked this message.

What this error means

Google documents this response as a message-content security rejection. Gmail may block executable files, blocked file types inside compressed archives, malicious macros, password-protected archives, and some links, images, or other message content. The message can be rejected even when it has no attachment.

This is different from Gmail 554 5.6.0, which reports a malformed message. It is also not evidence that SPF, DKIM, or DMARC failed.

Find the blocked item

  1. Save the full bounce and the original message.
  2. If the message has attachments, inspect every file inside archives. Check for executable content, macros, and password-protected archives.
  3. If there is no attachment, send a minimal plain-text test to a Gmail address you control. Then restore links, images, the signature, and other content one part at a time.
  4. When one item makes the test fail, remove or replace it. Scan any file before sharing it by another method.
  5. If the file is legitimate but Gmail blocks its type, upload it to an approved storage service such as Google Drive and send an access-controlled link.

Keep the test safe

Do not rename an executable, change only its extension, or hide it in another archive. Gmail checks compressed and nested content, and bypassing a security control puts the recipient at risk.

Frequently asked questions

Can SPF, DKIM, or DMARC fix Gmail 552 5.7.0?

No. This exact response concerns message or attachment content, not domain authentication.

Should I rename the blocked file extension?

No. Do not disguise unsafe content. Share a safe file through an approved storage service or remove it.

Will Gmail accept the same message if I retry it?

Usually not. This is a permanent rejection for that message. Correct the content and send a new message.

Related email diagnostics

Gmail 554 5.6.0: Email message is malformed. Not acceptedFix Gmail 554 5.6.0 by validating RFC message structure, headers, MIME boundaries, and the software generating email. SMTP 5.3.4: Message too big for systemFix SMTP 5.3.4 when a message exceeds the receiving system's size limit by reducing attachments or using a file link. Yahoo 554 Message not allowedResolve Yahoo 554 Message not allowed by using the full response to distinguish authentication, content, reputation, and sender-policy causes.

Primary sources: Gmail SMTP errors and codes, Gmail blocked file types.