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How Nylas Sends Emails

Nylas doesn't send emails from our servers. Instead, once you make the API call to send an email, we connect to the email server's SMTP with the user's credentials and upload the email for delivery.

One of three things then happens:

  • The email is accepted for delivery and we return a 200 response to your application.
  • The email is rejected by the email server. We'll pass along the rejection code and error message from the provider.
  • The email is delayed. This can happen if the email server is under heavy load or we're trying to upload a large attachment. We recommend waiting three minutes for the request to time out before sending any new API calls.

Email Delivery Services

An email delivery service sends emails on behalf of other domains. If your email administrator asks for information about Nylas, you can let them know that Nylas doesn't function as an email delivery service and we don't manage the following:

What's Next?

  • Dealing with Spam - While Nylas is not an email provider, we have a few tips on dealing with messages being marked as spam.