The web interface of Gmail prompts you to include an attachment if you reference one within the body of your message but do not include one with the email.

When you use Gmail with an email program like Microsoft Outlook or iOS Mail, the email program (and not Gmail) takes accountability for attachments. Although modern versions of Outlook do prompt similarly to Gmail, many don't, so you can't rely on Gmail's service alone unless you're using it directly on the web or in a dedicated Gmail mobile app.

How to Receive a Forgotten-Attachment Reminder

To get an alert from Gmail when you promise a file in your message but fail to attach any files, include the following phrases in the body of your message:

I have attached

I've attached

I have included

I've included

See the attached

See the attachment

Attached file

That's it — no special settings or configurations. Gmail parses the messages and will automatically flag when you've used a magic phrase without a file attachment.

We've prepared a step-by-step walk-through about sending attachments with Gmail in case you'd welcome a refresher.