How to Use the Gmail Promotions Tab in Postcards

Most marketing emails land in Gmail's Promotions tab and get treated as just another row of text — sender name, subject line, snippet. Easy to scroll past. But Gmail gives marketers a way to stand out: a rich preview card that shows a full banner image, your brand logo, a promo code, a discount badge, and even a countdown to expiration — all before the recipient ever opens the email.

Postcards now lets you configure that card directly inside the editor, without touching a single line of code. This guide explains what the feature does, how to set it up, what each card style is best for, and — just as importantly — what to realistically expect when you test it.

What Is the Gmail Promotions Tab, and Why Does It Matter?

When Gmail detects that an email is promotional — a sale, a newsletter, a campaign — it routes it to the Promotions tab. That's expected, and not necessarily a bad thing. The Promotions tab is where people go looking for deals.

The real opportunity is what happens inside that tab. Gmail can render your email in one of two ways:

• A plain text row — sender, subject, snippet. Functional, but invisible in a sea of other emails.
• A rich preview card — a large image, your logo, a promo code, an expiration date, even a swipeable product carousel. Much harder to ignore.

The difference between the two comes down to a small piece of hidden information embedded in the email's HTML. That hidden information tells Gmail: "here's the image to show, here's the offer, here's when it expires." Without it, Gmail defaults to the plain row. With it, Gmail may render the full card (learn how Gmail describes the Promotions tab).

Important: This is a Gmail-only feature. Outlook, Yahoo, Apple Mail, and every other inbox provider simply ignores the hidden annotations and shows the normal email. Adding them never hurts — it only helps Gmail readers.

The Four Card Styles

Postcards supports all four annotation formats that Gmail offers (see Gmail's annotation overview). You pick one per project based on what your campaign is trying to do.

Not sure which to pick? Start with Single Image if you have one strong visual, or Product Carousel if you're promoting multiple items.

1. Single Image

A large hero banner — ideal for a product launch, a seasonal sale, or any campaign built around one strong visual. You can include a click-through URL plus optional discount details: original price, percentage off, promo code, and expiration date.

Best for: Single-product launches, banner-style campaigns, big seasonal sales.

Image requirements: 1.91:1 aspect ratio, minimum 690 × 361 px.

2. Product Carousel

Up to 10 product tiles are displayed as a horizontal swipeable strip in Gmail's inbox. Each tile has its own image, product name, price, and link. When someone swipes through in Gmail on their phone, they're seeing your catalog before they've even tapped to open the email.

Best for: Multi-product collections, "shop the sale" emails, seasonal roundups.

Image requirements: 1:1 aspect ratio, minimum 460 × 460 px per product image.

3. Deal Annotation

A text-based badge that appears right next to the sender's name in the inbox — no big image required. It surfaces a promo code and deal description directly in the inbox row. Clean, fast, effective when the code itself is the headline.

Best for: Simple promo-code campaigns, flash sales, discount announcements.

4. Deal Card

A standalone card built around a single description and promo code. Gmail pulls the "From" name automatically, so there's no separate sender branding to configure. Think of it as the most focused format — nothing competes with the offer itself.

Best for: Quick single-offer messages, transactional-style promotions.

Setting It Up in Postcards: Step by Step

Step 1 — Open the Gmail Promotions Tab settings

At the right-hand side in Editor, you'll find a master toggle: "Gmail Promotions Tab. " It's off by default.

Flip it on when you're ready.

Step 2 — Turn the feature on

After it's turned on, you’ll see two options: “Edit Promotion” and “Preview Promotion.”

Clicking on “Edit Promotion” will take you directly to the Promotions tab editor on the right-hand side.

Good to know: Turning the toggle off later doesn't erase your configuration. Everything you've filled in stays saved. Flip it back on and it's all still there.

Step 3 — Pick your card style

Select one of the four card styles from the panel. You can switch between them freely — Postcards keeps all four configurations saved in the background simultaneously, so switching from Single Image to Product Carousel and back doesn't wipe out what you've already entered for either.

Step 4 — Fill in the fields

Each card style has its own set of fields. The screenshot below shows all four panels side by side so you can see exactly what you're working with.

The Single Image Preview panel is labeled with numbered callouts:

1. Promotion Type — Select the card style that best fits your campaign. You can switch between all four styles at any time — each one saves its settings independently, so switching never erases what you've already filled in.
2. Sender Details — Upload your brand logo and enter the email subject line. The logo appears next to your sender name in the Gmail inbox, building recognition before the recipient even opens the email.
3. Product Image — Upload the main hero banner and optionally add a click-through URL. Tapping the card in Gmail takes the recipient directly to that URL — no need to open the email first.
4. Promotion (Optional) — Add a headline, a discount percentage, and the original price. Postcards calculates the absolute discount amount Gmail requires automatically — you just enter the percentage and the base price.
5. Deal Details — Enter a short description of your offer and an optional promo code. This text surfaces directly on the card in the inbox, so recipients see the deal before opening.
6. Expiration Date — Toggle this on to attach a deadline to your promotion, adding urgency right in the inbox.

The other three card styles follow the same logic with slight variations:

Product Carousel note: Use the + button to add up to 10 product tiles. Enable the “Include Name and Price” option to display the product name and price directly in the inbox preview.

If this option is disabled, the annotations will appear differently, as shown below.

(See the Product Carousel section for reference when “Include Name and Price” is enabled.)

Postcards handles these automatically, so you don't have to:

• Image cropping and resizing — Pick any image from your existing Image Gallery. Postcards crops and scales it to Gmail's required dimensions automatically. Your original stays untouched in the gallery.
• URL fixing — Gmail requires https:// on all links. If you enter http:// or just example.com, Postcards rewrites it correctly at export time.
• Discount math — Enter a percentage off and the original price. Postcards converts it to the absolute amount Gmail's format requires.

Step 5 — Undo, Redo, Copy/Paste, and Collaboration

A few editor features worth knowing about:

Undo / Redo — Every change to your card configuration, including flipping the master toggle, is undoable with Cmd/Ctrl+Z. Typing in a text field is grouped into a single undo step (no letter-by-letter undo). Discrete actions like picking an image, switching card style, or pasting are their own undo steps.

Copy / Paste between projects — You can copy a finished Gmail Promotions Tab configuration from one project and paste it into another. The clipboard is tagged so it only pastes into the right place — it won't accidentally overwrite anything else.

Collaboration lock — If two teammates have the same project open at the same time, only one can edit the Gmail Promotions Tab panel at once. The second teammate sees a lock indicator on the panel. This prevents conflicting saves.

Auto-save — You never need to click Save. Every change is persisted automatically in the background. Typing is debounced (saves 5 seconds after you stop), but closing the panel flushes immediately, and discrete actions like picking an image save right away.

Step 6 — Preview the card

Click the Preview button to open a side-by-side mockup showing how your card will look in Gmail on iOS and Android.

If anything is required that is missing, the panel highlights the incomplete fields and explains what needs to be fixed. If everything is valid, the preview opens immediately.

Let's take the "Single Image Preview" card as an example.

Step 7 — Test it for real

This is where expectations need to be calibrated carefully — see the full section below on testing. The short version: send a test email to youraddress+promotabtesting@gmail.com to trigger Gmail's annotation rendering in a test environment.

Step 8 — Export as usual

Once your card is configured and your toggle is on, export your campaign exactly as you normally would — download HTML, push to your ESP (Mailchimp, Klaviyo, HubSpot, etc.), or copy to clipboard. The hidden annotation code is attached automatically.

One thing to keep in mind: for the card to actually appear in recipients' inboxes, your sending domain needs to be enrolled in Gmail's promotions program. This is a one-time setup handled directly with Google by your email  — nothing you need to do inside Postcards.

Testing Your Card: What to Expect (and What Not to Expect)

Testing Gmail Promotions Tab annotations is genuinely tricky, and it's important to set the right expectations before you spend time troubleshooting.

Why can't you test it in Postcards' built-in preview

The in-editor preview and public preview links don't include the annotation code. This is intentional — those previews are served from Designmodo's domain, and attaching annotation markup to emails sent from our domain could affect our sender reputation if the configuration is invalid. The card is for Gmail's servers to read, not a browser preview page.

The promotabtesting trick

Google provides a special address format for developers to test annotations in a real Gmail inbox (see Gmail's preview annotation guide). When you send a test email to an address ending in +promotabtesting@gmail.com, Gmail will attempt to render the annotation card.

Example: If your address is yourname@gmail.com, send a test to yourname+promotabtesting@gmail.com.

What you'll actually see — and why it varies

Even with the testing address, results can be inconsistent. Gmail's annotation rendering is controlled by Google's own algorithm, and the platform makes its own judgment call about whether to display the card based on:

• The sending domain — Gmail strongly favors corporate domains (e.g, yourbrand.com) over free Gmail addresses. Personal @gmail.comsenders are unlikely to trigger card display.
• The sender's reputation — Gmail evaluates whether the sending domain is enrolled in its promotions program and whether the email meets its quality signals.
• The email content — Gmail analyzes the body independently to decide whether it qualifies as promotional content.
• The recipient's device — The Promotions tab rich card only renders on mobile (Gmail iOS and Android). It does not appear on desktop Gmail.

The honest picture: Even with a correctly configured annotation and a properly enrolled domain, Gmail ultimately decides whether to show the card. The same email can render the card on one device and show a plain row on another. This is a Google constraint, not a Postcards one. Our job is to generate the correct annotation code — what Gmail does with it from there is up to their algorithm.

If you want to test with the highest chance of actually seeing the card, send through an ESP like Mailchimp using a corporate sending domain (yourbrand.com), and check on a mobile device. That's the setup closest to a real production send.

Plans and Access

The Gmail Promotions Tab feature is available to all users — free and paid. There's no paywall.

Anonymous (logged-out) users can't access Gmail Promotions features. The toggle is hidden for unauthorized users because the feature requires a team account to store the configuration.

Quick Reference Checklist

Before sending your campaign, confirm:

• Gmail Promotions Tab toggle is on
• Card style selected and all required fields filled in
• Preview checked in the Preview modal (iOS + Android mockup)
• Test email sent to +promotabtesting@gmail.com address and verified on a mobile device
• Campaign exported through your ESP with a corporate sending domain
• Sending domain enrolled in Gmail's promotions program (one-time, handled by your IT/email team)

Wrapping Up

The Gmail Promotions Tab card is one of those features that can meaningfully improve how your emails perform — but only if you understand what it does and doesn't guarantee. Postcards handles the technical side completely: generating valid annotation code, cropping images to spec, fixing URLs, calculating discounts, and attaching everything cleanly to your export. What happens after that is in Google's hands.

Set it up, test it properly, send it through a reputable domain, and let Gmail do its thing. When it renders, it's one of the most effective ways to make your email stand out before it's even opened.