Email API
Calendar API
Contacts API 
Scheduler
Notetaker API
Google email & calendar integration
Outlook email & calendar integration
IMAP integration
Google Meet integration
Zoom integration
Microsoft Teams integration
Docs
SDKs
Tutorials
API status
Changelog
Support
Blog
Events
Guides
Inspiration gallery
Build vs. buy
Customer stories
Security & Compliance
Why Nylas
Newsroom
Introducing Email Signatures for the Nylas Email API
• 5 min read
Sending emails through Nylas is straightforward. But replicating the signature experience that users get from Gmail or Outlook? Until now, that’s been entirely on the developer. Builders have had to wire up their own signature editors, storage, and insertion logic — just to match a feature that every email provider handles natively.
Today, that changes. The Nylas Email API now supports Email Signatures: store HTML signatures per user, and Nylas automatically appends them when sending emails or creating drafts. No custom storage layer, no insertion logic, no guesswork about where the signature goes. Just a signature_id in your send call.
Email signatures seem simple, but implementing them properly means solving several problems at once. Developers building on Nylas have had to build a UI for users to create or paste their signature, store those signatures per user in their own backend, determine which outgoing emails need a signature applied, and handle insertion in the right place within the email body.
That’s a significant chunk of application logic for something that most users take for granted. It’s especially painful for CRM and sales platforms, where branded, professional signatures are a core part of the outreach experience — not a nice-to-have.
With this release, signature management moves into the Nylas API. Here’s what’s now available:
Each signature has a name for labeling and a body containing the HTML content. Nylas handles sanitization and storage — you just pass the HTML in.
Create a signature for a user with a simple POST:
POST /v3/grants/{grant_id}/signatures
{
"name": "Work Signature",
"body": "<div><p><strong>Jane Smith</strong></p><p>Account Executive | Acme Corp</p><p><a href=\"mailto:[email protected]\">[email protected]</a></p></div>"
}Nylas returns a signature_id that you store alongside your user record. Then, when sending an email, include it in the request:
POST /v3/grants/{grant_id}/messages/send
{
"to": [{"email": "[email protected]"}],
"subject": "Following up",
"body": "<p>Hi — just wanted to circle back on our conversation.</p>",
"signature_id": "sig_abc123"
}That’s it. Nylas appends the signature after the email body. The same signature_id field works when creating drafts or sending an existing draft.
Email signatures are one of those features that users don’t think about until they’re missing. For the end user, a signature appearing on their outbound email is table stakes. For the developer, it’s been a disproportionate amount of work.
For developers, this means less custom code to write and maintain, faster time to a polished email experience, and one fewer thing standing between your integration and production.
For end users, it means their outbound emails look the same whether they’re sent from Gmail, Outlook, or your application.
The best way to get signatures into Nylas is through a settings page in your application. Give your users a place to create or paste their signature HTML — similar to the signature settings they’re already familiar with in Gmail or Outlook — and then store it via the API. From there, Nylas handles the rest: persisting the signature, sanitizing the HTML, and appending it at send time.
This approach gives you full control over the experience. You decide how users create their signatures, how many they can have (up to 10 per grant), and which signature gets applied to each email. Signatures support HTML with externally hosted images, so users can include logos, headshots, and branding just like they would in their provider. Your application passes a signature_id on each send or draft call, which means you can build smart defaults, let users pick per-email, or apply signatures automatically based on context — whatever fits your product.
Email Signatures are available now for all Nylas Email API users. Add signature support to your integration in minutes.
👉 Want to try it out? Sign in to your Nylas account or create a free Sandbox account to get started.
Explore the resources:
Today we’re launching Scheduler x Notetaker – bringing Notetaker controls into the Scheduler. This unlocks…
Today we’re launching Nylas Transactional Send into public beta, and it’s now available to all…
@nylas/connect is the solution to many of the manually setup hosted authentication snippets you’ve copy‑pasted over…
Product Manager