To optimize 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 strategies to ensure your messages are delivered, without being tagged as spam or junk.
Improve email deliverability
Section titled “Improve email deliverability”We recommend taking the following steps to improve your email 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
429error 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
Section titled “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
Section titled “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
Section titled “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.
Troubleshoot sending errors
Section titled “Troubleshoot sending errors”If messages you send using Nylas are consistently bouncing or being flagged as spam/junk, there are a few troubleshooting steps you can take:
- Confirm that messages bounce or are flagged as spam/junk only when being sent using Nylas. Try sending the same message using your provider’s web client.
- If the message is blocked when sent from the provider’s client, the issue occurs either because of the provider’s SMTP IP address or the sender’s domain reputation. Contact your email administrator to troubleshoot the issue further.
- Confirm that your project isn’t modifying the message headers. You should always use
Content-Type: application/jsonwith the Send Message endpoint. - If the provider is Google or Microsoft, find the list of hostnames and IP addresses in the message headers and check them using a blacklist check tool. If any are blacklisted, contact your email administrator and ask them to change the outbound SMTP server.
- Try sending the message with link clicked tracking disabled.
If none of these tips fix the issue, make sure the email address isn’t sending spam. If it is, the provider blocks sending on its own outbound server.
If you need help with troubleshooting your project’s deliverability, learn how to get support.