Email - Authentication

The core email protocols do not have any mechanism for authentication.

Messages must be authenticated to make sure that they're classified correctly. Also, unauthenticated messages are very likely to be rejected. Because spammers can also authenticate emails, authentication by itself isn't enough to guarantee that your messages can be delivered.

Tips for sending bulk messages with Gmail:

• Gmail combines user reports and other signals with authentication information when classifying messages. Authentication is mandatory for every email sender to ensure that your messages are correctly classified. For best practices, see Gmail's Bulk Senders Guidelines.
• Learn how to create a policy to help control unauthenticated emails from your domain.

First, make sure that messages that you've sent are authenticated using

• DKIM (preferred)
• or SPF.

Use RSA keys that are at least 1024 bits long. Emails signed with less than 1024-bit keys are considered unsigned and can easily be spoofed.

• getting-your-head-around-dkim-dmark-spf-and-ptr

• Check if your Gmail message is authenticated
• This message may not have been sent by…
• https://kb.mailpoet.com/article/151-email-authentication-spf-and-dkim
• https://www.convertingcopy.com/how-to-avoid-the-spam-folder-with-dkim-and-spf-authentication/
• https://mailchimp.com/help/my-campaign-from-name-shows-mcsvnet/