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Improving email deliverability with Nylas

To optimize message deliverability with Nylas, it’s important to contact your user base selectively rather than sending thousands of messages per day from a single grant. This page describes how to ensure your messages are delivered, and how to avoid being tagged as spam/junk.

Improve email deliverability

We recommend you take the following measures to improve message deliverability:

  • When you send a lot of messages in a group, space them out. We recommend you send them at most once every 30 seconds.
  • If a message doesn’t get through (for example, the Nylas API returns a 429 error code), wait before retrying. If it fails again, use an exponential backoff approach to prevent the account from being flagged or rate-limited on the provider.
  • Don’t send more than the recommended 700 messages per day from a single grant. Some providers lock the user’s account it if sends too many messages per day. For information on provider message limits, see Provider rate limits.

Avoid being tagged as spam or junk

Unsolicited messages are more likely to raise flags compared to sending a message to someone you already have an email history with. Check out Mailchimp’s Most Common Spam Filter Triggers guide for more information.

Google sender requirements

As of February 2024, Google requires that accounts sending more than 5,000 messages per day to Gmail addresses take the following steps to verify their authenticity:

  • Authenticate your email address’ domain using the Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and DMARC protocols.
  • Ensure that your domain or IP has valid forward and reverse DNS records.
  • Allow recipients to unsubscribe from mailing lists with a single click. The unsubscribe link needs to be clearly visible in the message body, and the request to unsubscribe must be processed within two days.

For more information, see Google’s official Email sender guidelines.

Microsoft filters and reputation

Microsoft Outlook has a rigid filter system as well as a reputation system. If a specific email address sends a lot of messages but doesn’t receive any replies, its reputation score decreases and Microsoft eventually tags it as a spam/junk sender. To avoid this, have recipients add your email address as a safe sender or as part of a safe mailing list.

If your messages are still tagged as spam/junk after a recipient marks them as safe, you might have a synchronization issue. This is usually solved by changing the account’s password.