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Prevent mail to Gmail users from being blocked or sent to spam

This article was previously called Bulk sender guidelines.

Use the guidelines in this article help ensure messages are delivered as expected to Gmail's inbox. The tips in this article reduce the likelihood that Gmail blocks messages, or marks 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 Google Workspace. Email addresses for Google Workspace work or school accounts don’t include @gmail.com.

Following the guidelines in this article reduces the chances that:

  • Gmail limits sending rates
  • Gmail blocks messages
  • Gmail marks messages as spam

Note: Gmail doesn't accept allowlist requests from third-party email senders. We can't guarantee messages will pass Gmail’s spam filters.

Using a Google Workspace account to send mail? Be sure to review the Spam and abuse policy in Gmail. This policy is part of the Google Workspace Acceptable Use Policy.

Problems not solved in this article

This article doesn't provide solutions to these issues:

Third-party email service providers

If you use a third-party email service provider with your domain, make sure the provider follows the guidelines in this article. Large email providers such as Google, AOL, and Yahoo, typically 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, don't include content about promotions 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 solarmora.com might have From: headers like this:
    • Purchase receipt messages: receipt@solarmora.com
    • Promotional messages: deals@solarmora.com
    • Account notification messages: alert@solarmora.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 other domains or senders without permission. This practice is called spoofing, and it can cause Gmail to mark 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 their inbox.

Make sure your messages are authenticated

Authenticated messages:

  • 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

Only send mail to people who want to get messages from you. 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. Learn about your domain’s reputation with Postmaster Tools.

Make sure recipients easily subscribe

Use these methods to help ensure you're sending to engaged users:

  • Make sure recipients opt in to get mail from you.
  • Confirm each recipient's email address before subscribing them.
  • Consider periodically sending messages to confirm recipients want to stay subscribed.
  • Consider unsubscribing recipients who don’t read your messages.

Let recipients unsubscribe

Always give recipients a way to unsubscribe from your messages. Make unsubscribing easy. Letting people opt out of your messages can improve message open rates, click-through rates, and sending efficiency.

Here are some recommended unsubscribe methods:

  • Include a prominent link in the message that takes recipients to a page for unsubscribing.
  • Let recipients review the individual mailing lists they’re subscribed to. Let them unsubscribe from lists individually, or all lists at once.
  • Automatically unsubscribe recipients who have multiple bounced messages.
  • Periodically send a confirmation message to recipients to make sure they still want to get your messages.

Use one-click unsubscribe

To let recipients unsubscribe while in Gmail, set up one-click unsubscribe. Include one or both of these headers in your messages:

List-Unsubscribe-Post: List-Unsubscribe=One-Click
List-Unsubscribe: <https://solarmora.com/unsubscribe/example>

If you include both headers, Gmail uses the one listed first.

When a recipient unsubscribes using one-click, you receive this POST request:

"POST /unsubscribe/example HTTP/1.1
Host: solarmora.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 26
List-Unsubscribe=One-Click"

Learn more about List-Unsubscribe headers:

Avoid these practices

  • Don't mark internal messages as spam. This can negatively affect your domain's reputation, resulting in future message being sent to spam.
  • Don’t purchase email addresses from other companies.
  • Don’t send messages to people who didn't sign up to get messages from you. These recipients might mark unwanted messages as spam. Future messages to these recipients will be marked as spam.
  • Avoid opt-in forms that are checked by default, which 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 using your email service (mail providers)

Note: The guidelines in this section are for email service providers.

When clients use your service to send email, you’re responsible for their sending practices. We recommend taking these steps to help manage clients sending activity:

  • Offer an email address for reporting email abuse, for example: abuse@mail-provider.com.
  • Maintain updated contact information in your WHOIS record and on abuse.net.
  • Immediately remove any 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. We recommend you 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:
    From: notifications@solarmora.com 
  • Include a valid Message-ID header field in every message (RFC 5322).
  • Links in the body messages should be visible and easy to understand. Recipients should know where they 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

Important: Increasing the sending volume too quickly can result in delivery problems. As you gradually increase your sending mail volume, use Postmaster Tools to monitor mail performance.

If you send large volumes of email, we recommend you:

  • Send mail at a consistent rate. Avoid sending mail in bursts.
  • Start with a low sending volume, and 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.

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 people who subscribe to your emails, and give recipients 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 Google Workspace domains. For example, you might send mail to users with email addresses that have the domains your-company.net and solarmora.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 Google Workspace or Gmail for sending: When you reach the sending limit, Google Workspace 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 recipients 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 Google Admin 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.

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