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Proton Mail signature: how to add, format and fix it

Add a signature in Proton Mail on the web, format it, fix images recipients cannot see, and remove the default mobile sign-off.
The Sendoff team4 min read

Sign in to account.proton.me, open Settings > All settings, select Identity and addresses, and scroll to Display name and signature. Type or paste your signature, then select Update. Proton adds it to the end of the messages you send from that address. The mobile app keeps its own signature, which says "Sent from Proton Mail mobile" until you change it on a paid plan.

How do I add a signature in Proton Mail on the web?

  1. Sign in to account.proton.me.
  2. Go to Settings, then select All settings.
  3. Select Identity and addresses in the sidebar.
  4. Scroll to Display name and signature.
  5. Type or paste your signature into the signature field, then select Update.

If you have more than one address, select Email address and pick the address first. Each address can have its own signature. The signature you save becomes the default for that address, and you can still change or remove it for a single message.

How do I format the signature?

The toolbar under the signature field changes the text style, size and colour. It also adds images, lists and quotes, according to Proton's help page.

Proton's help page also describes a route for a signature made in another tool: copy the signature from the builder, paste the text or code into the Signature field, then select Update. I could not find Proton documentation that says how its editor handles HTML tables from a builder. Send a test message to a second account and check the layout there before you rely on it.

Why don't my signature images show for recipients?

Proton's help page says recipients need load remote content turned on in their email provider's settings before they see images in your signature. That setting is on the recipient's side, so you cannot change it from your account. Send a test to an account you control. If the image is missing for a recipient, ask them to check that setting.

Why does "Sent from Proton Mail mobile" appear under my signature?

Proton adds a mobile signature to every email sent from an iPhone, iPad or Android device. By default it says "Sent from Proton Mail mobile". What you can change depends on your plan:

  • Free: you cannot edit or turn off the mobile signature. You can add a regular signature, and Proton shows it in addition to the mobile one.
  • Paid: open the Proton Mail app, go to ≡ > Settings > Signature > Mobile signature, then edit the text or switch it off.

Why does my HTML signature look wrong in the mobile app?

Proton's help pages do not say whether the mobile app uses the HTML from your web signature. A user request posted in October 2023 says it did not. An HTML signature set on the web did not show in mail sent from the app, and pasting the same HTML into the mobile field looked "kind of all over the place". The request had 39 votes when I read it, and I found no official fix. If you need the signature on mobile, keep its formatting simple and send a test from the app.

Why does a link vanish in replies to plain text emails?

A Proton community request from 6 October 2025 says that an HTML signature with a linked call to action appears in replies to plain text messages, but without the link. The request asks for a "do not use in plain text" option. It had 3 votes when I read it. I did not test a workaround, so check the reply from a second account before you depend on the link.

How Sendoff handles this

  • Sendoff builds the signature from HTML tables with inline CSS, so the styling travels inside the HTML you paste.
  • Copy signature puts the formatted HTML on the clipboard. Copy HTML copies the raw code for editors that accept HTML.
  • A live size meter counts the HTML against 10,000 characters. That is the Gmail limit. The Proton help pages I read do not state a limit, so treat the meter as a guide.
  • Sendoff has no Proton-specific install page. Build the signature in the free signature generator, paste it into the Proton field, and check the result as described above.

What this guide does not cover

Proton's digital signatures are a cryptographic feature that proves a message came from you and was not changed. They are not the email sign-off you add in settings. Proton's page on that feature is linked in the sources.

Sources

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