How to Enable Protection From Unusual File Types in Gmail Attachments

Check Protect against anomalous attachment types in emails.

Under Choose an action, decide what to do with emails caught by this rule:

• ​Keep email in inbox and show warning (default)
• Move email to spam
• Quarantine

If you select Quarantine, click Choose a quarantine to select a quarantine to use for this. See how to create and access quarantines here.

You can whitelist file types if needed under Whitelist the following uncommon filetypes. They should be listed without a period, followed by a space and a comma, like this:

jpg, gif, pdf (except these file types are not uncommon)

After updating, click SAVE at the bottom. Changes may require up to 24 hours to take effect.