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Check an attachment before sending with Proton Mail

Attach a harmless file in Proton Mail Free, preview its contents and remove the wrong copy before sending your real message.

HoldMyTwist · 2 min read

Two aqua files clipped to a navy envelope

A filename can look correct while the file contains the wrong draft. Open the attachment inside Proton Mail before sending a real message.

This Free web-app example uses a fictional text file and stops before sending.

Before you start

You need a Proton account for the Mail web app. Create a Proton Mail Free account (opens in a new tab) or sign in with your existing account. Have a small, harmless practice file ready. This exercise stops before sending.

1. Create a practice draft

  1. Open Proton Mail (opens in a new tab).
  2. Click New message.
  3. Enter Practice attachment check as the subject. Leave the recipient empty for practice.
  4. Prepare a small practice-plan.txt with harmless text, such as: Fictional practice plan. Status: first draft.

2. Attach the exact file

  1. Click the paperclip Attachments button.
  2. Choose practice-plan.txt in the file picker.
  3. Wait for upload to finish. Expand the attachment details if only a file count appears.

Proton Mail attached practice text file with Show and Hide attachment details

Proton Mail attached practice text file with Show and Hide attachment details
Open full-size image

Watch out

Check the file itself, not only its name. Proton limits outgoing attachments to 25 MB in total, and email encoding adds size. Leave room below the limit. The receiving service can impose its own smaller limit, so uploading an attachment is not a delivery guarantee.

If your file is too large to attach, see how to share a Proton Drive file without recipient signup. Check that you have enough Drive storage. The guide uses a public link without a password, so anyone who gets it can download the file. Revoking the link won't remove downloaded copies.

3. Read the attached copy

  1. Click the attachment's filename to preview it.
  2. Check its opening text and version. This example says first draft.
  3. Close the preview. If the file is wrong, hover over its tile and use Remove, then attach the correct one.
  4. Close and reopen the saved practice draft to check that the attachment remains.

Proton Mail preview of the attached fictional first draft

Proton Mail preview of the attached fictional first draft
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Before sending a real message

Check the recipient, subject and attachment again. Send only when you intend to deliver that content. A saved draft has not been sent; this example makes no delivery claim.

If preview is unavailable for the file type, download the attached copy and inspect it with the appropriate app.

If you need a Mail account for this exercise, create a Proton Mail Free account (opens in a new tab) and practise with the harmless text file above. Leave the recipient empty until you intend to send a real message.

Sources: Attachment controls and limits (opens in a new tab); Attachment previews (opens in a new tab); Large-file sharing (opens in a new tab).

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