Prevent mail to Gmail users from being blocked or sent to spam
The guidelines in this article help ensure your messages are delivered to Gmail's inbox. Use the tips in this article to reduce the likelihood that Gmail blocks your messages or marks your messages as spam
These guidelines are for anyone who sends email to Gmail users. A Gmail user is anyone with one of these Gmail account types:
- A personal Gmail account, ending in @gmail.com.
- A work or school Gmail account from G Suite. Email addresses for G Suite work or school accounts don’t include @gmail.com.
Following the guidelines in this article reduces the chances that:
- Gmail limits your sending rate
- Gmail blocks your messages
- Gmail marks your messages as spam
Note: Gmail doesn't accept whitelisting requests from mail senders. We can't guarantee messages will pass Gmail’s spam filters.
This article does not provide solutions to these issues:
- Bounced mail to one user: If you’re getting bounced messages when sending to a single Gmail user, learn how to fix bounced emails.
- Message rejected by Google Groups: If your message is rejected when sending to a work or school Google group, go to sender guidelines for work or school accounts.
If you use an email service provider for your domain
If you use an email service provider with your own domain, make sure the provider follows the guidelines in this article. Large email providers, for example Gmail, AOL, and Yahoo, generally follow these guidelines.
If you use a domain provider but you manage your own email service, we recommend you:
- Review and follow the best practices in this article for sending email to Gmail users.
- Use Postmaster Tools to monitor information about messages sent from your domain to Gmail users.
Follow best practices for sending to Gmail
To reduce the chances that messages from your domain are sent to spam or blocked by Gmail, follow the general best practices in this section.
Set up valid reverse DNS records of your IP addresses that point to your domain.
Ideally, send all messages from the same IP address. If you must send from multiple IP addresses, use different IP addresses for different types of messages. For example, use one IP address for sending account notifications and a different IP address for sending promotional messages.
Don't mix different types of content in the same messages. For example, you shouldn't include content about upcoming sales in purchase receipt messages.
Messages of the same category should have the same email address in the From: header. For example, messages from a domain called your-company.net might have From: headers like this:
- Purchase receipt messages: email@example.com
- Promotional messages: firstname.lastname@example.org
- Account notification messages: email@example.com
Check regularly to make sure your domain isn’t listed as unsafe with Google Safe Browsing. To check your domain status, enter your domain in the Safe Browsing site status page. Also, check any domain that’s linked to yours.
Don’t send sample phishing messages or test campaigns from your domain. Your domain’s reputation might be negatively affected, and your domain could be added to internet blocklists.
Don’t impersonate another domain or sender without permission. This practice is called spoofing, and it can cause Gmail to categorize the messages as spam.
To help prevent valid messages from being marked as spam:
- Messages that have a From address in the recipient’s Contacts list are less likely to be marked as spam.
- Occasionally, valid messages might be marked as spam. Recipients can mark valid messages as not spam, so future messages from the sender should be delivered to the inbox.
Make sure your messages are authenticated
- Help protect recipients from malicious email, like phishing messages.
- Are less likely to be rejected or marked as spam by Gmail.
These authentication methods are set up at your domain provider. If you use a domain hosting service or an email provider, use the provider's instructions for setting up authentication. Set up authentication for each of your sending domains.
To minimize the chance that your messages are marked as spam, set up these authentication methods:
- Publish an SPF record for your domain. SPF prevents spammers from sending unauthorized messages that appear to be from your domain.
- Turn on DKIM signing for your messages. Receiving servers use DKIM to verify that the domain owner actually sent the message. Important: Gmail requires a DKIM key of 1024 bits or longer.
- Publish a DMARC record for your domain. DMARC helps senders protect their domain against email spoofing.
For SPF and DKIM to authenticate a message, the message From: header must match the sending domain. Messages must pass either the SPF or the DKIM check to be authenticated.
Send email to engaged users
Send mail only to users who choose to get and read your messages. They’re less likely to report messages from your domain as spam.
If messages from your domain are often reported as spam, future messages are more likely to be delivered to the spam folder. Over time, many spam reports can lower your domain’s reputation.
Get detailed information about your IP and domain’s reputation with Postmaster Tools.
Make sure users subscribe
Use these methods to help ensure you're sending to engaged users:
- Make sure users opt in to get mail from you.
- Confirm each recipient's email address before subscribing them.
- Consider periodically sending messages to confirm users want to stay subscribed.
- Consider unsubscribing users who don’t read your messages.
Let users unsubscribe
Always give users a way to unsubscribe from your messages, and make unsubscribing easy. Letting users opt out of your messages can improve message open rates, click through rates, and sending efficiency.
These are some recommended unsubscribe methods:
- Include a prominent link in the message that takes users to a page for unsubscribing.
- Let users review the individual mailing lists they’re subscribed to. Let them unsubscribe from lists individually, or all lists at once.
- Automatically unsubscribe users who have multiple bounced messages.
- Periodically send a confirmation message to users to make sure they still want to get your messages.
Use one-click unsubscribe
To let users unsubscribe while in Gmail, set up one-click unsubscribe. Include one or both of these headers in your messages:
If you include both headers, Gmail uses the one listed first.
When a user unsubscribes using one-click, you receive this POST request:
"POST /unsubscribe/example HTTP/1.1
Learn more about List-Unsubscribe headers:
Avoid these practices
- Don’t purchase email addresses from other companies.
- Don’t send mail to users who didn't sign up to receive messages from you. These recipients might mark unwanted messages as spam. Future messages from your server to these users are marked as spam.
- Avoid opt-in forms that are checked by default and that automatically subscribe users. Some countries/regions have restrictions for automatic opt-in. Check the laws in your country/region before opting-in users automatically.
Monitor senders who use your email service
Note: This best practice is for email service providers.
When senders use your email service to send mail, you’re responsible for the sender’s email activity. You should:
- Provide an email address for message recipients to report email abuse, for example: firstname.lastname@example.org
- Maintain updated contact information in your WHOIS record and on abuse.net.
- Immediately remove any user or client who sends spam with your service.
Monitor affiliate marketers
Affiliate marketing programs offer rewards to companies or individuals that send visitors to your website. However, spammers can take advantage of these programs.
If your brand is associated with marketing spam, other mail sent by you might be marked as spam. You should monitor affiliates, and remove any affiliates that send spam.
Format your messages for inbox delivery
These message formatting guidelines increase the likelihood that Gmail delivers your messages to the inbox, not to the spam folder:
- Format messages according to the Internet Format Standard (RFC 5322).
- If your messages are in HTML, format them according to HTML standards.
- Don’t use HTML and CSS to hide content in your messages. Hiding content might cause messages to be marked as spam.
- Message From: headers should include only one email address, as shown in this example:
- Include a valid Message-ID header field in every message (RFC 5322).
- Links in the body messages should be visible and easy to understand. Users should know where they’ll go when they click links.
- Sender information should be clear and visible.
- Message subjects should be relevant and not misleading.
- Format international domains according to the Highly Restrictive guidelines in section 5.2 of Unicode Technical Standard #39:
- Authenticating domain
- Envelope from domain
- Payload domain
- Reply-to domain
- Sender domain
Increase sending volume slowly
If you send many messages, we recommend you:
- Send mail at a consistent rate. Avoid sending mail in bursts.
- Start with a low sending volume, then slowly increase the volume over time.
- As you increase the sending volume, regularly monitor the sending rate and any responses you get. Regular monitoring lets you turn down the sending volume when the sending rate is limited, or when you start seeing errors.
As you gradually increase your sending mail volume, use Postmaster Tools to monitor mail performance.
Important: Increasing the sending volume too quickly can result in delivery problems.
These factors affect how quickly you can increase sending volume:
- The amount of email sent: The more email you send, the more slowly you should increase sending volume.
- The frequency of sent email: You can increase the sending volume more quickly when you send daily instead of weekly.
- Recipient feedback about your messages: Make sure you send only to users who subscribe to your emails, and give users an option to unsubscribe.
Follow recommended IP practices
Follow these best practices for mail servers that send email to Gmail users:
Verify the sending server PTR record
Important: The sending IP address must match the IP address of the hostname specified in the Pointer (PTR) record. PTR records are also called Reverse DNS records.
Your sending IP address must have a PTR record. PTR records verify that the sending hostname is associated with the sending IP address. Every IP address must map to a hostname in the PTR record.
Check for a PTR record with the intoDNS tool.
Monitor your sending volume
Important: For work and school accounts, sending limits apply even when recipients are in different G Suite domains. For example, you might send mail to users with email addresses that have the domains your-company.net and other-company.com. Although the domains are different, if both domains have google.com as their MX record, messages sent to these domains count toward your limit.
If you use G Suite or Gmail for sending: When you reach the sending limit, G Suite limits the message sending rate for that IP address.
Follow these recommendations to help stay within the sending IP limits:
- Be aware of email sending limits when sending from domains that have a Google.com MX host.
- Limit sending mail from a single IP address based on the MX record domain, not the domain in the recipient email address.
- Monitor responses so you can change sending rates as needed to stay within these limits.
Monitor shared IP address reputation
A shared IP address (shared IP) is an IP address used by more than one mail sender. The activity of all senders on the shared IP impact the reputation of everyone using the IP.
If you use a shared IP for sending mail, any other sender’s negative reputation negatively affects your reputation. A negative reputation can impact your delivery rate.
If you use a shared IP for sending mail, we recommend these steps:
- Make sure the IP address isn’t on any internet blocklist. Messages from sending IPs on a blocklist can be marked as spam.
- If you use an email service provider for your shared IP, use Postmaster Tools to monitor the reputation of the shared IP.
Use Postmaster Tools to monitor sent mail
Use Postmaster Tools to get information about the mail you send to Gmail users, for example:
- When users mark your messages as spam
- Why your messages might not be delivered
- If your messages are authenticated
- Your domain or IP reputation and its impact on message delivery rates
Troubleshoot mail delivery problems
If you use an email service provider
If you use an email service provider and you’re having delivery problems, contact your provider. Find out if they use the best practices in this article.
Use MX Toolbox to review domain settings
Use the G Suite Toolbox to check and fix settings for your domain.
Fix the source of rejected email
If your messages are rejected, you might get an error message. Learn more about the error so you can fix the problem. Common error messages are:
- 421, "4.7.0": Messages are rejected because the sending server’s IP address is not on the allowed list for the recipient’s domain.
- 550, "5.7.1": Messages are rejected because the sending server’s IP address is on an IP suspended list. You might get this error if you’re sending mail using a shared IP with a poor reputation.
Learn more about email and SMTP error messages:
Fix IPv6 authorization errors
An IPv6 authorization error could mean the PTR record for the sending server isn’t using IPv6. If you use an email service provider, confirm they’re using an IPv6 PTR record.
Here's an example of an IPv6 authorization error:
550-5.7.1: Message does not meet IPv6 sending guidelines regarding PTR records and authentication.
Use the troubleshooting tool
If you’re still having mail delivery problems after following the guidelines in this article, try Troubleshooting for senders with email delivery issues.