If you send emails that are blocked or experience problems with Gmail delivery, follow these guidelines to help them get classified correctly.
- If you see the Gmail error message, 'Message rejected by Google Groups', go to senders guidelines for work or school accounts.
- If you're sending to an individual, learn how to fix bounced emails.
How Gmail classifies incoming emails
- Spam: Spam goes to the Spam folder; everything else goes to the inbox.
- Inbox categories: In Gmail's default inbox layout, messages are divided into the following categories:
Email classifications automatically adjust to match users' preferences and actions. For example, users can unmark spam, move messages to a different category, or switch categories on or off. Over time, Gmail automatically adjusts classifications according to these corrections. Find out more about inbox categories.
Step 1: Use Postmaster Tools
Postmaster Tools provides metrics on reputation, spam rate, feedback loop and other parameters that can help you identify and fix delivery or spam filter issues.
Step 2: Make sure that emails are classified correctly
- Send consistently from the same address for each email category. For example, always send promotional emails from one address and financial transactions from another address.
- Avoid mixing different categories in one message. For example, if you include promotional content in an email with a financial transaction, Gmail could classify the email as promotional.
Step 3: Make sure that emails are not marked as spam
Emails without authentication often get blocked or marked as spam to protect recipients from phishing scams. Unauthenticated emails with attachments might get completely rejected for security reasons.
To ensure Gmail can authenticate you:
- Send from the same IP address.
- Keep valid reverse DNS records of your IP address that point to your domain.
- Choose the same address in the 'From:' header for every message.
- Sign messages with DKIM. We don't authenticate messages signed with keys that use fewer than 1024 bits.
- Publish a SPF record.
- Publish a DMARC policy.
Learn more about email authentication.
- The sending IP must have a PTR record (i.e. a reverse DNS of the sending IP) and must match the IP obtained via the forward DNS resolution of the hostname specified in the PTR record.
- The sending domain should pass either a SPF check or DKIM check.
Include option to subscribe
- Provide each recipient on your distribution list with either 'opt-in' option below:
- An email asking them to subscribe
- A tick box on a web form or in software they need to manually tick
- Confirm each recipient's email address is correct before subscribing them.
- Purchasing an email address from a third party
- Including a tick box on a web form or in software that is automatically ticked and subscribes users by default
When users receive a lot of emails they don’t open, Gmail will show a card with the option to unsubscribe.
Allowing users to unsubscribe can improve open rates, click-through rates and spend efficiency. Learn about how users unsubscribe from emails.
A user must be able to unsubscribe from your mailing list in one of the following ways:
- Make sure that recipients can unsubscribe through either:
- A prominent link in the body of an email leading to a confirmation page, without requiring recipients to provide additional information
- An option to reply to your email to unsubscribe
- To make sure that recipients can unsubscribe without leaving Gmail, we strongly recommend adding a 'List-Unsubscribe' header in one of the following ways:
- Add the following headers for one-click unsubscribe as described in RFC 8058:
If the recipient unsubscribes, you'll get this POST request:
"POST /unsubscribe/opaquepart HTTP/1.1
- Point to an email address using 'mailto:'
Note: If both options are added to the List-Unsubscribe header, Gmail will use the method specified first.
- Automatically unsubscribe users whose addresses bounce multiple times.
- Occasionally send confirmation messages to users.
- Include each mailing list that recipients are signed up for, and give them the option to unsubscribe from any that they're no longer interested in.
To take care of any emails your recipients forward, we recommend that you:
- Explicitly indicate the email address subscribed to your list.
- Support a URL method of unsubscribing from your mailing list. This is particularly helpful if your mailing list manager can't tell who is unsubscribing based on the 'Reply-to:' address.
Format your emails
Make sure your messages have:
- Formatting according to RFC 5322 and, if using HTML, HTML standards
- A valid 'Message-ID:' header field
- An indication that you're sending emails in the 'Precedence: bulk' header field
- Visible information about the true sender and true landing page for links
- Subject lines that are relevant to the message content and not misleading
- Domain formatting according to the highly-restrictive Unicode Security Profile guidelines for international domain names, including:
- Authenticating domain
- Envelope From domain
- Payload domain
- Reply-to domain
- Sender domain
Follow delivery tips
Important factors for delivery
While Gmail works hard to deliver all legitimate emails, it's possible that some legitimate messages get marked as spam.
Here are factors that normally help deliver messages to Gmail recipients:
- The 'From:' address matches someone in the recipient's Contacts.
- If your message is welcome but accidentally sent to spam, the recipient can click Not spam.
Note: Gmail doesn't accept 'whitelisting' requests from senders, and can't guarantee that all of your messages will bypass our spam filters.
Promotional emails or financial transactions
To help improve the chances of getting important promotional or transactional emails to your recipient, we recommend separating emails by purpose as much as possible. For each type of email (promotional or transactional), you can:
- Use separate email addresses
- Send emails from different domains and/or IP addresses
Monitor third-party senders
If others use your service to send emails (for example: ISPs), you are responsible for monitoring your users and clients' behaviour. Make sure you:
- Provide an email address to your users and/or clients to report abuse (for example, firstname.lastname@example.org)
- Maintain up-to-date contact information in your WHOIS record and on abuse.net
- Quickly terminate all users and clients who use your service to send spam
Monitor affiliate marketers
Affiliate marketing programmes reward third parties for bringing visitors to your site. Unfortunately, spammers can take advantage of these programmes.
If your brand becomes associated with affiliate marketing spam, it can affect the emails sent by you and your other affiliates. It is your responsibility to monitor your affiliates and remove them if they send spam.