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Improve email deliverability with Nylas

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

Improve email deliverability

Nylas recommends doing the following to improve your email deliverability:

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

For information on how Exchange throttling works behind the scenes, see Microsoft's official Understanding Client Throttling Policies documentation.

Avoid being tagged as spam or junk

Unsolicited messages are more likely to raise flags compared to emailing an address you already have an email history with. Check out Mailchimp's guide to common spam filter triggers for more information.

Microsoft filters and reputation

Microsoft Outlook has a rigid filter system and a reputation system. If a specific email address sends a lot of email messages but doesn't get any replies, its reputation score decreases and it is eventually tagged 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 email messages are still tagged as spam/junk after a recipient marks them as safe, you might have a synchronization issue that can be solved by changing the account's password.

Google sender requirements

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

  • Authenticate your email address' domain using 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 only one click. The unsubscribe link must 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.

Video walkthrough

Prefer video? You can watch our Coding with Nylas livestream.