ProtonMail’s attachment reminders prevent you from accidentally sending emails to your recipient without including the relevant attachments. When you mention keywords such as “attachments” or “attached” in your email without attaching a file, ProtonMail automatically displays the following message:
If you wish to include an attachment in your email before sending it, click Cancel and add your attachment.
This feature is currently supported in the English, German, French, Spanish, and Russian languages. ProtonMail will only display this message if you use keywords in your account language. For example, you will not see an attachment reminder for a French keyword if your account language is set to English.
Note: Keyword detection is done locally (client-side) — only you can read the contents of your email before it is sent to your recipient. ProtonMail does not have access to your emails and cannot read your messages.