A good-looking preview is only one test
An HTML email can render beautifully in a preview and still fail to reach the inbox. Design checks answer whether the message is readable. Delivery checks ask whether it was accepted by the receiving system, where it arrived and whether the sender is authenticated.
Keep these as separate sign-off items. For example, fixing a broken button layout does not repair a missing DNS record, and a successful authentication result does not prove the mobile layout is usable.
Verify the real sending service
Identify which platform sends the campaign and which domain appears in the From address. A website’s contact form, staff mailbox and marketing platform may be separate senders. Each needs the appropriate configuration.
As checked on 29 October 2026, Gmail’s sender guidelines require SPF or DKIM for all senders to personal Gmail accounts, with SPF, DKIM and DMARC required for bulk senders. Additional requirements apply to relevant marketing and subscription messages, including unsubscribe behaviour. Read the current rules for your sending volume rather than treating this summary as the full checklist.
Use your provider’s verification tools and an actual delivered test message to inspect authentication. Do not paste arbitrary DNS values from a tutorial into a production domain.
Send the same message through the production path
Use the actual sending platform, template and From address for a controlled test to inboxes you own. A screenshot exported from the design tool is not equivalent. Check the sender name, subject, preview text, images, links and reply destination.
- Open the message on a phone and a desktop.
- Check whether the message reached the inbox or another folder.
- Review the authentication results in the message details.
- Follow the main link and confirm the destination works.
- Test the unsubscribe flow on a designated test subscription.
Do not send the test to a customer list just to see what happens. Keep test contacts clearly labelled and use safe destinations for forms and payment links.
Record the cause before changing the template
If a message is missing, look for a sending log, rejection or bounce first. If it arrived but is unreadable, inspect the HTML and client-specific rendering. If a link fails, check its destination and tracking rewrite. These are different failures with different owners.
For HTML email development, agree whether the scope includes only template coding or also platform integration and delivery testing. No template can guarantee inbox placement, but a documented test process can reveal problems before a wider send.