The Email section near the bottom of the builder panel controls the message your recipients receive. It shows the current subject as a preview, and expands so you can edit it.
The default subject is built from the expiry date: something like ✍️ Please sign until 22 Sep 2026, 20:00.

Why change it
Your recipient is receiving an email from a company they may not know, asking them to click a link and then prove their identity. Everything that makes it recognisable helps it get opened rather than deleted.
- Name the document. "Consulting agreement: Northwind Legal" tells them what this is. The default deadline wording does not.
- Name yourself or your company. They are looking for a sender they recognise.
- Say why now if there is a reason, a deadline, a meeting it needs to be signed before.
What language it goes out in
Your company language sets the default for everything swipesign sends your signers. If you mostly write to German-speaking clients, set it once and stop thinking about it. See Language settings.