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Check if your Gmail message is authenticated

If you see a question mark next to the sender's name, the message isn't authenticated. When an email isn't authenticated, that means Gmail doesn't know if the message is coming from the person who appears to be sending it. If you see this, be careful about replying or downloading any attachments.

Check if a message is authenticated

Note: Messages that aren't authenticated aren't necessarily spam. Sometimes authentication doesn't work for real organizations who send mail to big groups, like messages sent to mailing lists.