552 5.7.0: blocked for a potential security issue
Gmail blocked the message because something in it, typically an attachment, looks like a security risk under its content and attachment rules.
- Gmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 552 5.7.0
- Provider
- Gmail and Google Workspace
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
552 5.7.0 This message was blocked because its content presents a potential security issue.
What it means
Gmail checks attachments and content for malware and for file types it does not allow. Google links this reply to its article on file types blocked in Gmail. Gmail rejects the whole message, attachment and all. Renaming a file's extension is not a reliable way around it, since Gmail also checks files inside archives. Share the file another way, or remove whatever triggered the block and send again. Google documents this reply twice with almost identical wording.
Common causes
- An executable or script file attached, even inside an archive.
- A document or file that Gmail flags as potentially harmful.
- Content that matches known malware or phishing.
How to fix it
- 01Check the attachments against Google's list of file types blocked in Gmail.
- 02Share executables, scripts and other blocked types through a file sharing link instead.
- 03Scan the files for malware before sending, since a block can mean a file is infected.
- 04Resend without the blocked item.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Gmail SMTP errors and codes (Google Workspace Admin Help)knowledge.workspace.google.com
Related codes
- 421 4.7.0Suspicious content or links.Gmail blocked this message because something in its text or its links looks like spam or abuse to Gmail's filters.
- 552Storage allocation exceeded.The receiving server aborted the message because it exceeded a storage limit, usually a full mailbox or a message larger than allowed.
- 5.7.0Security or policy refusal, unspecified.The message or session was refused for a security or policy reason that the server did not describe more precisely, or chose not to reveal.
5.7.0 at other providers
All 108 Gmail codesEvery code in the wikiPaste your own bounce