For Gmail's sender guidelines, see Email sender guidelines.
Causes of delivery failure
Delivery failures usually occur for one or more of the following reasons:
Sending too many emails.
A sudden increase in the number of emails sent.
Sending emails to unknown spam honeypot addresses.
Sending emails to invalid addresses.
The outbound IP address is on a blocklist.
Emails are reported or marked as spam by Gmail users.
Using a new IP address to send emails without a warm-up period.
Incomplete or incorrect DNS records for the domain name.
Failed email identity verification.
Including special types of attachments or links to IP addresses.
Actions to take based on the latest Google delivery recommendations:
1. Verify your domain name:
Google requires that emails have an authenticated identity. If you send more than 5,000 emails from a root domain, you must configure the following three protocols.
a. SPF record
Purpose: Prevents malicious actors from using your sending account on the Direct Mail platform to send fraudulent notifications and promotional messages.
How to configure: Go to your DNS provider and modify the TXT record for your domain name according to the configuration table in the Direct Mail console.
For more information, see How to configure an email domain.
b. DKIM record
Purpose: DKIM is an email security protocol that authenticates the sending domain name through message encryption. It also checks whether an email was altered during transit to ensure the integrity of the body.
How to configure: Go to your DNS provider and modify the TXT record for the specific DKIM domain name according to the configuration table in the Direct Mail console.
For more information, see What is DKIM? How do I set up a DKIM record?
c. DMARC record
Purpose: Prevents spoofing. DMARC instructs recipients on how to handle forged emails and provides reports about the forgeries.
How to configure: Go to your DNS provider and add a TXT record with the following format: v=DMARC1;p=none;rua=mailto:a***@example.net;ruf=mailto:a***@example.net. You must configure the email addresses for the rua and ruf parameters.
For more information, see What is DMARC? How do I set up a DMARC record?
2. Add an unsubscribe option
Gmail requires marketing senders who send more than 5,000 emails per day to provide recipients with a one-click unsubscribe button. For more information, see Help with the unsubscribe feature.
3. Use Google Postmaster Tools to continuously monitor the reputation and spam rate of your domain name on the management page. To verify ownership of your domain, add the specific value provided by Gmail to your DNS configuration. For more information, see Related help.
Google requires that the spam rate be kept below 0.1%. If the rate exceeds 0.3%, Google will impose penalties. These penalties can lower your domain's reputation, which can cause subsequent emails to be rejected or sent to the spam folder.
Data in Postmaster Tools is delayed. You must wait two to three days to view the delivery status and reputation for a specific day. Postmaster Tools does not display information if your sending volume is too low. To ensure data is displayed, you must send more than 500 emails per day.
4. Use a warm-up plan to gradually increase your sending volume. For more information, see Warm-up recommendations.
5. Check your domain's status with Google.
6. Use troubleshooting tools
If you still have email delivery problems after you follow the guidelines in this topic, troubleshoot email delivery issues for senders.