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You must follow these guidelines if your application is sending out bulk email, that is, similar messages to numerous recipients. These guidelines will help to improve your inbox delivery rate to Gmail users, by ensuring that all recipients in your distribution list actually want to receive the email. If recipients manually mark your email as spam, then that acts as a strong signal to Gmail to mark future emails from you as spam.
For more information on sending mail, see the Mail API Overview.
This API is supported for first-generation runtimes and can be used when upgrading to corresponding second-generation runtimes. If you are updating to the App Engine Python 3 runtime, refer to the migration guide to learn about your migration options for legacy bundled services. Authentication and identificationFrom
header will be set to match the sender you specify.Unauthorized sender
error message.apphosting.bounces.google.com
domain, so your SPF record may not be used to determine if email from App Engine should be delivered.Each user in your distribution list should opt-in to receive messages from you in one of the following ways:
Using an email address list purchased from a third party is not considered opt-in. You also should not set a checkbox on a web form or within a piece of software to subscribe all users by default. Users should not be required to explicitly opt out of mailings.
You should verify that the person that signed up by checking the box on the web form or in software is actually receiving emails at the address that was specified in the form. Verify the user by sending an email that requires them to confirm receipt.
[APP_ID].appspotmail.com
domain. Therefore, you will need to set your sender to an address in this domain if you want to automatically handle email unsubscribe responses within App Engine.List-Unsubscribe
header, which is supported by the App Engine Mail API.From
address is listed in the user's Contacts list.abuse@[YOUR_DOMAIN].com
. You should also monitor postmaster@[YOUR_DOMAIN].com
.If you send too many emails in a short burst, some emails might be silently dropped due to Google safety limits. To avoid this, calculate the maximum daily rate of emails sent per second by dividing your daily quota by 86,400, the number of seconds in a day. Do not send bulk email at a rate higher than 50 times the maximum daily rate.
For more information on other quotas around sending mail, see Quotas and limits.
What's nextExcept as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2025-08-07 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-07 UTC."],[[["These guidelines are essential for improving email delivery rates to Gmail users when sending bulk emails, emphasizing the importance of recipients' consent and avoiding spam practices."],["Using the same sender for bulk emails, ensuring it's a Google Workspace account, signing emails with DKIM, and publishing an SPF record are crucial for authentication and preventing spam spoofing."],["Users must actively opt-in to receive emails, either by requesting subscription or manually checking a box, and the practice of purchasing email lists or pre-selecting opt-in boxes is strongly discouraged."],["Clear and easy unsubscription methods must be provided, including a prominent unsubscribe link, email response handling, and the use of the `List-Unsubscribe` header."],["Maintaining proper email formatting according to RFC 2822 SMTP and w3.org standards, avoiding URL shorteners, and providing relevant subject lines are necessary to ensure email deliverability."]]],[]]
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