# What is nyl.as?

Source: https://developer.nylas.com/docs/dev-guide/platform/what-is-nyl/

You might occasionally come across a link in a message or on the web that has `https://nyl.as/` in it. These links redirect to another page on the internet. Links to `nyl.as` are part of our [message tracking feature](/docs/v3/email/message-tracking/) — they generate a notification when someone clicks the link. In normal use they're not malicious or a security issue.

> **Warn:** 
> **If you find a `nyl.as` link that redirects to spam or a malicious website, report it to [**Nylas Support**](https://support.nylas.com/hc/en-us/requests/new)**. We'll take immediate action to fix the issue.

## `nyl.as` errors on older devices

Some devices might receive "Certificate not trusted" errors (or other related errors) if they try to access `nyl.as` links. This is because they don't support [Let's Encrypt certificates](https://letsencrypt.org/2023/07/10/cross-sign-expiration). For more information, see [Nylas domain certificates](/docs/dev-guide/platform/nylas-domain-certificates).