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The tips in this article reduce the likelihood that Gmail blocks messages, or marks messages as spam.
These guidelines are for anyone who sends emails 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:
Bounced mail to one user: If you’re getting bounced messages when sending to a single Gmail user, read 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.
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 emails 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 emails, 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 to them.
Consider periodically sending messages to confirm recipients want to stay subscribed.
Consider unsubscribing recipients who don’t read your messages.
Avoid these practices
Don't mark internal messages as spam. This can negatively affect your domain's reputation, resulting in the future messages 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.
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 number of emails 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 DNS tool.
Monitor your sending volume
Important: For work and school accounts, sending limits to 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.
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:
SMTP error reference
Fix bounced or rejected emails
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