Mobile Email Rendering Issues

There's nothing worse than crafting a beautiful email and then seeing it look completely off on a phone. Maybe things don't line up, fonts change, or you have to scroll sideways to read anything.

Here's a helpful guide to common mobile email display problems and how to fix them using the tools built into the Postcards Email Builder, so your emails always look great, whether they're viewed on a desktop or a smartphone.

Common Mobile Display Problems

When your email is opened on a mobile device, you might see things like:

Zoomed-out or sideways scrolling: Your email looks tiny, or users have to scroll sideways to read it.
Misaligned sections or cropped images: Menus or footers shift, images zoom in, or get cut off.
Fonts not loading: Custom fonts like Recoleta or Poppins don't appear and are replaced by basic ones.
Buttons not working: Your call-to-action buttons may not respond or preview incorrectly.
Layout breaks: Fixed-width elements or complex tables may look fine on desktop but break on mobile.

How Postcards Handles Mobile Width

Before jumping into fixes, it helps to understand how Postcards treats width across desktop and mobile views, since this is where most rendering issues actually come from.

There are two different "width" concepts in the editor that often get confused:

1. The main container width

This is the overall canvas width of your template (600px by default). This setting controls how the canvas displays in Desktop view inside the editor only.

It does not control how your template adapts on mobile after export. Changing it won't fix or break responsive behavior on phones, its job is purely to set the desktop canvas size.

2. The width of individual elements

This is the width applied to specific elements inside your template, text blocks, images, Grid items, buttons, and so on. These are the values that actually drive how your email renders on mobile.

In Mobile view, Postcards works against an implicit mobile width of around 375px (the standard reference width for mobile devices). If an element has a fixed pixel width that exceeds that space once padding is included, the responsive layout can break.

When you add a module from the left panel, its elements are usually set to auto or a percentage width, which means they automatically adjust to fit the canvas (600px on desktop, 375px on mobile). Sticking with these defaults gives you the smoothest responsive behavior. Issues tend to start when fixed pixel widths are set manually and exceed the mobile canvas.

Easy Fixes To Try First

Here's how to fix mobile rendering issues in Postcards without diving into code:

1. Use auto or percentage widths on individual elements

For most elements, leave the width set to auto or use a percentage (like 100%) so they scale naturally to the canvas width on both desktop and mobile.
Avoid fixed pixel widths on elements unless you're certain they fit within the 375px mobile canvas, including padding.

2. Check elements in Mobile view inside the editor

Switch to Mobile view in Postcards before exporting. If an element looks like it's stretching past the canvas edge, that's a clear visual cue that its width needs to be adjusted.
Keep in mind that the container width field shown in Mobile view doesn't actually do anything to the export, focus on the per-element widths instead.

3. Keep layouts simple

Replace heavy tables or complex stacks with Grid and Group modules for cleaner, more responsive layouts.
Use the Fill option in modules to center content and avoid side scrolling.

4. Use Export as Image for tricky sections

If a section or module just won't behave on mobile (like a font-heavy header with a complex layout), export it as an image to lock in the design. Simply select the module and enable Export as Image in the settings panel to the right.

5. Watch out for background images

Background images can shift or get cropped on mobile. If a logo or graphic is set as a background image and disappears on mobile, try adjusting its Background image position in Mobile view (top-left usually works well), or swap it for an inline image instead.

Platform-Specific Tips

Important: both Gmail and Outlook can strip mobile-specific styles, which means emails sometimes appear on mobile devices the same as on desktop (with some differences). This isn't something we can fix on our side, it's a limitation on Gmail's and Outlook's end.

For the mobile layout to render properly, emails need to be sent through a third-party ESP rather than pasted directly into Gmail or Outlook.

Gmail (mobile and app)

Gmail tends to scale emails gracefully to the device width, so responsive templates usually look great here. Just keep in mind Gmail may strip out some mobile-specific styles when emails are imported through certain ESPs.
For best results, send your template through the Integrations feature (e.g. Mailchimp, Zoho, Constant Contact) rather than pasting raw HTML, since some ESP editors re-wrap or strip parts of the code.

Outlook mobile

Outlook mobile is stricter than Gmail. If an element has a fixed pixel width larger than the device viewport, Outlook will often render the full desktop width and add a horizontal scroll bar instead of adapting the layout.
This makes per-element widths even more important when sending to Outlook users, favor auto and percentages, and double-check Mobile view before exporting.
For Outlook, export using OFT or EMLTPL via the Outlook Template option when possible.
Background images can be unreliable in Outlook mobile, so use them sparingly or replace with inline images.

Apple Mail (iOS)

Apple Mail uses the WebKit rendering engine, which generally handles modern HTML and CSS well, so Postcards templates tend to look closest to the editor preview here.
Custom fonts and background images are usually supported, making it the most forgiving of the major mobile clients.
Even though Apple Mail renders cleanly, always test here too, it's the default mail app on iPhone, so a large portion of your audience will likely open emails through it.

Dark Mode On Mobile

Dark mode is one of the trickier parts of mobile email design, since most people now use it at least some of the time. The catch is that every email client handles dark mode differently, Gmail mobile applies its own color adjustments, Apple Mail on iOS tends to use partial inversion (keeping images mostly intact), and Outlook can range from full inversion to no change at all depending on the version. None of these can be disabled or overridden from the sender's side, so the most reliable approach is to design templates that hold up gracefully no matter which transformation gets applied.

A few quick things to keep in mind for mobile:

Avoid pure white (#FFFFFF ) and pure black (#000000 ) backgrounds, since these trigger the most aggressive inversion on mobile clients. Soft off-whites and near-blacks behave much more predictably.
Use transparent PNGs for logos so they blend cleanly with whatever background the client applies.
Keep strong text contrast (WCAG AA or higher) so text stays readable even after color shifts.
Watch out for dark logos or text on white backgrounds, they often become hard to see once a client inverts the background.

You can also preview how your template will look in dark mode directly from Postcards.

Click the eye icon then Preview & Share in the top toolbar

Then use the moon icon to switch the preview to Dark mode, and the phone icon to switch to Mobile view.

This gives you a quick way to spot contrast or readability issues before sending.

For a full breakdown of dark mode design techniques, here's a complete guide: https://help.designmodo.com/article/476-dark-mode-email-design

Final Tips For Great Mobile Emails

To make sure your emails shine on mobile:

Stick with auto and percentage widths on individual elements; reserve fixed pixel widths for cases where you're sure they fit within 375px.
Don't rely on the main container width to fix mobile issues, it only affects the desktop canvas inside the editor.
Use Grid and Group modules instead of complex custom layouts.
Add web-safe fallback fonts and test buttons in preview mode.
Export tricky sections as images when needed.
Always test on multiple devices and clients (Gmail, Outlook, Apple Mail) before sending, rendering can vary significantly between them.

And if anything still doesn't look right, Postcards support is just a click away. We'll help make sure your mobile emails look as polished as your desktop ones.