How to Preview Your Template Across Email Clients in Postcards

You've built a beautiful email template. It looks perfect in the editor. You export it, send a test, open it in Gmail — and something's off. A column breaks, a font substitutes, a button shifts. The problem isn't your design. The problem is that every email client renders HTML differently, and without seeing those differences before you send, you're flying blind.

Postcards now solves this with Email Client Preview — a built-in tool that generates real screenshots of your template across up to 46 email clients, so you can catch rendering issues before your campaign goes out. No exports needed, no third-party accounts to juggle. Just select your clients, generate, and see exactly what your subscribers will see.

Why This Feature Exists

Until now, the only way to check how your Postcards template looked in a real inbox was to export it and test it manually. That's slow, breaks the creative flow, and still doesn't cover the full range of clients your audience actually uses.

The built-in editor preview shows how your email renders in a browser — useful, but not the same as how Outlook 2016 or Gmail on iOS actually displays it. Email clients have their own rendering engines, their own quirks, their own dark mode behaviors. What looks flawless in Chrome can fall apart in Outlook.

Email Client Preview bridges that gap by generating actual screenshots of your template rendered in real email environments — so you know what you're shipping before you ship it.

What You Can Preview

Postcards gives you access to 46 email clients across three categories:

Desktop clients — All major Outlook versions (2003 through 2019), eM Client, Postbox, Windows Live Mail, Windows 10 Mail in both light and dark mode, and more.

Web clients — Gmail (Chrome and Firefox), Outlook.com (Chrome, Firefox, Dark Mode), Yahoo Mail, AOL Mail (Chrome, Firefox, and Basic), GMX, and others.

Mobile clients — iPhone models across generations, iPad, Android devices, and more — all shown at actual device dimensions.

How to Generate Previews: Step by Step

Step 1 — Open Email Client Preview

In the editor, click the eye icon in the top-right corner. A dropdown menu will appear — select Email Clients Preview.

Step 2 — Check your generation runs

Before selecting clients, you'll see a counter showing how many generation runs you have remaining for the current month and when they reset.

A few things worth knowing about how the counter works:

Generating previews uses one run, regardless of how many clients you select in that batch.
If a generation fails and no previews are produced, the counter does not decrease.
Retrying the same clients within the same version does not use an additional run.

If you've made changes to your template since the last generation, Postcards will show a warning: "Template modified since last run — Generating will use 1 run." This is a heads-up so you don't accidentally spend a run on a version you didn't intend to generate. If you proceed, Postcards will save the new results as a new version — so your previous previews stay intact, and you can compare before and after.

Generation runs reset monthly, on the same date as your export limit.

Note: Email Client Preview is available on paid plans. The number of monthly generation runs depends on your plan. Check the Postcards pricing page for current limits.

Step 3 — Select your email clients

Click Select Clients to open the client selection modal.

You have 46 clients to choose from. A few ways to narrow down your selection:

Quick Select filters at the top let you instantly pick a curated group:

Most Popular — the clients your audience is most likely using
Problematic — clients known for rendering issues (Outlook, we see you)
Dark Mode — clients that support dark mode rendering
iOS — all iPhone and iPad clients
Android — Android mail clients
Outlook — every Outlook version in one click

You can combine filters, manually check individual clients, or click Select All to run all 46 at once. When you're satisfied with your selection, click Done.

Step 4 — Generate

Back in the main panel, click Generate [number of] Previews.

Postcards sends your template to be rendered across all selected clients. Depending on how many clients you've selected, this takes a moment. Once complete, the results load as a grid of screenshots sorted by Client Popularity — the clients most commonly used by email recipients appear first.

For a quick look without opening the full preview, each thumbnail has a three-dot menu that gives you four options directly from the grid: Preview the screenshot in a lightbox, Copy Link to share it instantly, Download it as a PNG.

Skip This Client to mark it as skipped if it's not relevant to your campaign. Skipped clients remain visible in the grid but can be run at any time by clicking Click to Run directly on the thumbnail.

If a client fails to load during generation, the three-dot menu will show a Retry option — allowing you to re-run that specific client without generating a full new batch.

Step 5 — Review your previews

Click any thumbnail to open the full-screen preview for that client.

From here you can:

Navigate between clients using the left and right arrow keys or the on-screen arrows. The counter in the top center (e.g., "8 of 46") shows where you are in the sequence.

Check Known Issues — the Known Issues button in the top-left corner flags any documented rendering limitations specific to that email client. If something looks off and you're not sure whether it's your template or the client, this is the first place to check.

Copy a shareable link — the Copy Link button in the top-right generates a link to this specific preview. Share it with a teammate or a client for sign-off without them needing access to the editor.

Download the screenshot — the Download button saves the preview as a PNG file. Useful for documentation, client approvals, or keeping a record of how your email looked before sending.

Versions: Comparing Iterations

Every time you generate a new batch of previews, Postcards saves it as a Version. The version selector at the top of the preview screen lets you switch between past generations.

This means if you fix a rendering issue and regenerate, you can switch between Version 1 and Version 2 side by side to confirm the fix actually worked — without losing your original reference.

One thing worth knowing: versions are permanent. There's no option to delete individual versions, and they aren't removed when your monthly generation runs reset. The only time versions are deleted is when the project itself is deleted. So your entire preview history stays intact for as long as the project exists — which makes it a reliable record of how your template looked at each stage of production.

What to Look for When Reviewing

Not all rendering differences are bugs — some are just client-specific behaviors. Here's what's worth paying attention to:

Outlook (any version) — Outlook uses Microsoft Word's rendering engine, not a standard browser engine. This makes it the most likely place for layouts to break: multi-column structures, custom fonts, background images, and certain button styles are all common problem areas. Use the Problematic quick-select filter to see Outlook and other historically tricky clients together.

Dark Mode — Clients like Outlook.com in dark mode and Windows 10 Mail in dark mode can invert or recolor parts of your email that weren't designed with dark mode in mind. Check that your logo and images still look correct, and that text remains readable.

Mobile clients — Your email may look perfect on a desktop, but have text that's too small, buttons that are too close together, or images that don't scale correctly on mobile. Reviewing iPhone and Android screenshots tells you what the majority of your audience actually experiences.

Font fallbacks — If your template uses a custom font, some clients will substitute a system font. Check that the fallback doesn't break your layout or change the visual weight of your headings significantly.

Quick Reference Checklist

Before sending your campaign, use Email Client Preview to confirm:

No layout breaks in Outlook 2016, 2019, or Outlook.com
Dark mode versions look intentional, not broken
Mobile clients (iPhone, Android) display correctly at device size
Custom fonts degrade gracefully with fallback fonts
Images scale correctly across both mobile and desktop
Any issues flagged in Known Issues are addressed or accepted

Wrapping Up

Sending an email without previewing it across clients is a bit like publishing a website without checking it in different browsers — something will look different from what you intended, and you won't know until it's too late.

Email Client Preview gives you a clear view of your template across the full range of real environments before a single email is sent. Combined with the speed of building in Postcards, it closes the loop between designing and shipping: build it, preview it across 46 clients, fix what needs fixing, and send with confidence.