Proton Mail is built around privacy, and that shapes how signatures behave — both when you create them and when your recipients see them.
Here is where the setting lives, how to add a logo that actually displays, and the limitations worth knowing before you design around them.
Signatures in Proton Mail are attached to an address, not to the account as a whole.
Because signatures are per-address, an account with several addresses can carry a different signature on each — useful if you run separate personal and business identities from one mailbox.
The editor is a rich-text field with the usual formatting controls: fonts, sizes, colours, alignment and links. For anything more structured than a few lines of text, build the signature elsewhere and paste it in as formatted content rather than fighting the toolbar.
Paste a rendered signature, not raw HTML code. Copy from a preview so the editor receives formatting rather than markup.
Insert images by URL and make sure the address starts with https://. Images referenced from your computer will show for you and break for everyone else.
Keep the logo modest — around 150 to 200 pixels wide is plenty — and export it at twice that size so it stays sharp on high-resolution screens. Our guide to blurry logos in email signatures explains why.
Free accounts append a short line promoting Proton Mail beneath your own signature. It appears automatically and sits below whatever you have written.
The option to turn it off is available on paid plans, in the same identity settings area. If you are sending business email from a free account, be aware that every message carries that line.
This is the part that surprises people. Proton blocks remote content by default to prevent tracking, and other privacy-minded clients do the same. Your recipient may see the signature with every image suppressed until they choose to load it.
Design for that. Never place your name, job title, phone number or address inside an image. Give every image alt text that reads sensibly on its own. A signature that still works with no images at all is a signature that works everywhere.
Proton inserts the signature on replies and forwards as well as new messages. If you prefer a shorter version on replies, the practical approach is to keep the main signature compact enough that repetition on a long thread does not become noise.
Long threads are also where signature weight matters most — see our size guide for the limits.
None of these are dealbreakers. They just push you toward a simpler, sturdier signature — which is usually better anyway.
Design your signature with the Mail Ink generator and you get a clean version with hosted images and alt text already in place, ready to paste into Proton Mail — and into Gmail, Outlook or anything else you use alongside it.