Make Gmail automatically show images I embed in my HTML email?

Question

I'm constructing HTML emails in PHP with Zend_Mail and I'd like to embed/attach/whatever some images in such a way that Gmail will automatically display them without prompting the user. How can I do this?

Answer 1

Google's Bulk Sender Guidelines say that Gmail will automatically show images for senders who have authenticated their domain:

To ensure that Gmail can identify you:

• Use a consistent IP address to send bulk mail.
• Keep valid reverse DNS records for the IP address(es) from which you send mail, pointing to your domain.
• Use the same address in the 'From:' header on every bulk mail you send.

We also recommend publishing an SPF record, and signing with DKIM or DomainKeys.

By authenticating, inline images you send will be shown automatically. Recipients will not need to click the "Display images below" link.

Google offers a page to learn more about email authentication.