Email Signature on Mobile: How to Set Up and Optimize for Any Device

A mobile email signature is a block of contact information, branding, and links that appears at the end of emails sent from a phone or tablet. It serves the same purpose as a desktop signature but must be formatted for smaller screens, touch interactions, and the rendering limitations of mobile email apps.

According to Litmus's 2025 Email Client Market Share report, over 41% of all emails are now opened on mobile devices, with Apple iPhone alone accounting for roughly 34% of total email opens. This means nearly half of your recipients will see your signature on a screen that is only 320 to 428 pixels wide.

This guide walks you through setting up email signatures on every major mobile platform: iPhone, Android, Gmail app, Outlook mobile, and Samsung Email. You will also learn how to optimize images, avoid common formatting problems, and decide when a simplified mobile-only signature makes sense.

Why Your Mobile Email Signature Matters

Most professionals check and reply to emails on their phones throughout the day. A signature that looks great on a desktop monitor can turn into a broken mess on a mobile screen. Images may not load, text can overflow, and links can become impossible to tap.

A well-optimized mobile email signature ensures your contact details, brand, and calls to action display correctly no matter where your recipient reads your message. This is not just about aesthetics. Broken signatures undermine trust and make your emails look careless.

The good news is that fixing these problems does not require advanced technical skills. Each mobile email client has its own signature settings, and once you understand the constraints, you can build a signature that works everywhere.

How to Add an Email Signature on iPhone (iOS Mail App)

The built-in Mail app on iPhone uses a plain text signature editor. It does not support images, HTML, or rich formatting natively. Here is how to set it up.

Step-by-Step Instructions

1. Open the Settings app on your iPhone
2. Scroll down and tap Mail
3. Tap Signature (near the bottom of the Mail settings screen)
4. Choose All Accounts to use one signature across every email account, or select Per Account to customize signatures for each account individually
5. Type your signature text in the field
6. Tap the back arrow to save automatically

What You Can Include

The iOS Mail signature editor supports plain text only. You can type:

• Your full name
• Job title and company name
• Phone number
• Website URL (displayed as text, not a clickable hyperlink)
• A simple text divider like dashes or pipes

Adding an HTML Signature on iPhone

If you want images, links, or styled formatting in your iPhone signature, you need to use a workaround:

1. Create your HTML signature on a desktop computer or use a tool like Signkit
2. Send yourself an email that contains only the signature HTML
3. Open that email on your iPhone
4. Select all the signature content and copy it
5. Go to Settings > Mail > Signature
6. Paste the copied content into the signature field

This method preserves images and formatting because iOS Mail pastes rich content. However, the signature editor still shows it as plain text. The actual rendering will include your images and links when you compose new emails.

For a detailed walkthrough of Apple Mail signatures across all Apple devices, see our Apple Mail email signature guide.

How to Add an Email Signature on Android

Android does not have a single universal mail app. The two most common options are the Gmail app and Samsung Email. Each handles signatures differently.

Gmail App on Android

1. Open the Gmail app
2. Tap the hamburger menu (three horizontal lines) in the top left
3. Scroll down and tap Settings
4. Select the email account you want to modify
5. Tap Mobile Signature
6. Type your signature text in the dialog box
7. Tap OK to save

The Gmail mobile app signature is separate from your desktop Gmail signature. Whatever you set here only applies to emails sent from the app. Your desktop signature (configured at gmail.com) remains unchanged.

Important: The Gmail app on Android only supports plain text signatures. You cannot add images, HTML, or formatting directly. If you need a richer signature, consider using a signature management tool that injects your signature server-side, so the same signature appears regardless of which device you use.

For a complete guide to Gmail signatures on both desktop and mobile, read our Gmail email signature setup tutorial.

Samsung Email App

Samsung devices come with a built-in Email app that offers slightly more flexibility than the Gmail app.

1. Open the Samsung Email app
2. Tap the hamburger menu and then Settings (gear icon)
3. Select your email account
4. Tap Signature
5. Toggle the signature switch to On
6. Type or paste your signature text
7. Tap Save

Samsung Email supports basic rich text editing. You can apply bold, italic, and underline formatting. Some versions also allow inserting images directly, though rendering can be inconsistent depending on the recipient's email client.

How to Set Up a Signature in the Outlook Mobile App

The Outlook mobile app (available on both iOS and Android) has its own built-in signature editor that is separate from Outlook desktop or Outlook on the web.

Step-by-Step Instructions

1. Open the Outlook app on your phone
2. Tap your profile picture or initials in the top left corner
3. Tap the gear icon (Settings) in the bottom left
4. Under the Mail section, tap Signature
5. You will see a text editor with your current signature (the default is "Get Outlook for iOS" or "Get Outlook for Android")
6. Clear the default text and type your custom signature
7. Tap the checkmark or navigate back to save

Formatting Options

The Outlook mobile signature editor supports basic rich text:

• Bold, italic, and underline
• Hyperlinks (highlight text, then tap the link icon)
• Text size adjustments

It does not support inserting images directly into the signature editor. If you need images, you have two options:

1. Paste from a rich email: Create the signature on desktop, email it to yourself, copy the rendered version, and paste it into the Outlook mobile signature field
2. Use an organization-wide signature tool: Solutions like Signkit can deploy signatures that render consistently across Outlook desktop and mobile

If your organization uses Microsoft 365, administrators can also set server-side signatures through Exchange transport rules, which override client-side signatures entirely.

For the full Outlook signature setup process on desktop and web, see our Outlook email signature guide.

How to Set Up a Signature in the Gmail Mobile App (iOS)

The Gmail app on iOS works almost identically to the Android version, with one key difference in navigation.

1. Open the Gmail app on your iPhone or iPad
2. Tap your profile picture in the top right corner
3. Tap Settings (or Manage your Google Account, then navigate to Gmail settings)
4. Select the account you want to configure
5. Tap Signature settings
6. Toggle Mobile Signature on
7. Type your signature text
8. Tap Done or navigate back to save

Like the Android version, this signature only applies to emails sent from the Gmail mobile app. Your desktop signature configured at gmail.com is a completely separate setting.

Pro tip: If you want the same signature on both desktop and mobile Gmail, you will need to set it up in both places manually. Alternatively, use a centralized signature management platform that handles deployment across all clients and devices automatically.

Desktop vs. Mobile Signature: Key Differences

Understanding the differences between desktop and mobile signatures helps you decide whether to use the same signature everywhere or create separate versions for each context.

Content and Formatting

Desktop email clients (Outlook for Windows, Apple Mail on Mac, Gmail on the web) offer full HTML rendering with support for tables, inline styles, images, and complex layouts. Mobile clients strip or simplify much of this formatting.

A desktop signature might include a company logo, a headshot photo, social media icons, a promotional banner, and multiple lines of contact information. On mobile, this same signature can look overwhelming, take up too much screen space, and force recipients to scroll past your branding just to read the email.

Screen Real Estate

A desktop screen is typically 1200 to 1920 pixels wide. A mobile screen is 320 to 428 pixels wide. A signature designed for desktop takes up a small fraction of the visible area. On mobile, that same signature can occupy the entire screen or more.

Rendering Engines

Each mobile email client uses a different rendering engine:

• iOS Mail uses WebKit and renders HTML signatures well
• Gmail app strips many CSS properties and can break complex layouts
• Outlook mobile uses its own rendering engine that handles basic HTML but struggles with advanced CSS
• Samsung Email has inconsistent rendering across device models and OS versions

When to Use a Simplified Mobile Signature

Consider creating a separate, simpler mobile signature when:

• Your desktop signature includes large banner images or promotional content
• You frequently reply to emails from your phone (short replies with a massive signature feel disproportionate)
• Your signature includes multiple columns or complex table layouts that break on small screens
• You are sending from a personal device where you want a lighter professional presence

A mobile-optimized signature might include only your name, title, phone number, and a single link. No images, no banners, no social icons. Clean, fast, and readable.

Responsive Design Tips for Mobile Email Signatures

If you want a single signature that works across both desktop and mobile, follow these responsive design principles.

Keep the Width Under 600 Pixels

The standard maximum width for email content is 600 pixels. For mobile optimization, design your signature to look good at 320 pixels wide (the narrowest common mobile viewport). Use percentage-based widths or a maximum width of 600px with fluid scaling.

Use a Single-Column Layout

Multi-column signature layouts (such as a photo on the left and text on the right) often break on mobile. Columns stack unpredictably, and side-by-side elements can get squeezed into unreadable strips.

A single-column, vertically stacked layout is the safest approach:

1. Name and title
2. Contact details
3. Logo or image (if needed)
4. Social links

Size Images Correctly

Image sizing is one of the most common sources of mobile signature problems. Follow these guidelines:

• Maximum image width: 320px for mobile compatibility (see our email signature dimensions guide for full specifications)
• Logo dimensions: 100 to 200px wide, with a height that maintains the aspect ratio
• Headshot photos: 80 to 100px square
• Social media icons: 20 to 24px square
• Banner images: 320px wide maximum, or use a fluid width that scales down

Always set both width and height attributes on image tags. This prevents layout shifts while images load and gives email clients the information they need to reserve the correct amount of space.

Use Inline CSS Only

Mobile email clients (especially Gmail) strip <style> tags from the email head. All styling must be applied inline using the style attribute on each HTML element. This includes font sizes, colors, padding, and alignment.

<td style="font-family: Arial, sans-serif; font-size: 14px; color: #333333; padding: 0 0 4px 0;">
  Jane Smith
</td>

Make Links and Phone Numbers Tappable

On mobile, users interact with touch, not mouse clicks. Ensure that:

• Links have enough padding around them (minimum 44px tap target per Apple's Human Interface Guidelines)
• Phone numbers use tel: links so they are directly callable
• Email addresses use mailto: links
• Social media icons are at least 24px with spacing between them to prevent accidental taps on the wrong icon

Use Table-Based HTML

CSS layout properties like flexbox and grid are not reliably supported in email clients. Use nested HTML tables to structure your signature layout. This approach is the most compatible across both desktop and mobile email clients.

<table cellpadding="0" cellspacing="0" border="0" style="max-width: 600px; width: 100%;">
  <tr>
    <td style="padding: 10px 0;">
      <!-- Signature content here -->
    </td>
  </tr>
</table>

Mobile Signature Comparison: Features by App

Not all mobile email apps are created equal. Here is how the four most popular mobile email clients compare in their signature capabilities.

Feature	iOS Mail	Gmail App	Outlook Mobile	Samsung Email
Plain text signatures	Yes	Yes	Yes	Yes
Rich text editor	No	No	Yes (basic)	Yes (basic)
HTML signature support	Via paste workaround	No	Via paste workaround	Limited
Image insertion	Via paste only	No	No	Yes (some versions)
Multiple signatures	Yes (per account)	Yes (per account)	Yes (per account)	Yes (per account)
Syncs with desktop	No	No	No	No
Hyperlink support	Via paste only	No	Yes	Yes
Signature for replies	Same as new mail	Same as new mail	Same as new mail	Same as new mail
Server-side override possible	Yes (Exchange)	Yes (Google Workspace)	Yes (Exchange)	Yes (Exchange)

Key takeaway from this table: No major mobile email app syncs your mobile signature with your desktop signature automatically. They are always separate settings. This is one of the strongest arguments for using a centralized signature management tool that handles deployment across all devices.

Common Mobile Signature Problems (and How to Fix Them)

Images Not Loading

Problem: Your signature images appear as broken icons or empty boxes.

Causes and fixes:

• Blocked by default: Many email clients block external images until the recipient clicks "load images." Use hosted images with descriptive alt text so recipients see meaningful placeholder text
• Incorrect image URLs: Ensure your image URLs use HTTPS and point to a reliable hosting service. Self-hosted images on personal servers can go down
• Base64 embedded images: Some mobile clients strip or fail to render Base64-encoded images. Always use externally hosted image URLs instead

Formatting Breaking on Mobile

Problem: Your signature looks perfect on desktop but appears jumbled, oversized, or misaligned on mobile.

Causes and fixes:

• CSS properties stripped: Gmail's mobile app aggressively strips CSS. Move all styles to inline attributes
• Fixed-width elements: Replace width: 600px with max-width: 600px; width: 100% so elements scale down on smaller screens
• Multi-column layouts: Switch to a single-column layout that stacks vertically

Oversized Signatures

Problem: Your signature takes up more space than the actual email content on mobile.

Causes and fixes:

• Too many elements: Reduce your mobile signature to essential information only. Name, title, phone, one link
• Large images: Resize images for mobile. Logos should be no wider than 150px. Banners should be no wider than 320px
• Excessive padding: Reduce padding and margins in your signature HTML. Mobile screens need tighter spacing

"Sent from my iPhone" Appearing Above Your Signature

Problem: The default iOS signature "Sent from my iPhone" shows up alongside your custom signature.

Fix: Go to Settings > Mail > Signature and delete the default text before adding your custom signature. If you see both, you may have the default on one account and a custom signature on another. Switch to "Per Account" view to check each one.

Signature Not Appearing on Replies

Problem: Your signature shows on new emails but disappears on replies or forwards.

Causes and fixes:

• Some email clients only insert the signature on new messages by default. In Gmail desktop settings, verify that you have a signature selected for both "For new emails use" and "On reply/forward use"
• On mobile, most apps apply the same signature to all outgoing messages including replies. If yours is missing, check that the signature setting is toggled on and not empty

Best Practices for Mobile Email Signatures

Keep It Short

Aim for four to six lines of text maximum. On a mobile screen, every extra line of signature content pushes the actual email further away. Prioritize: name, title, phone, and one link.

Test on Multiple Devices

Send test emails to yourself and open them on different devices and email apps. At minimum, test on:

• iPhone (iOS Mail)
• Android phone (Gmail app)
• Outlook mobile
• Desktop Gmail (to see how your mobile-sent emails look to desktop recipients)

Use a Consistent Brand Across Devices

Even if your mobile signature is simpler than your desktop version, maintain the same visual identity. Use the same font choices, the same color for links, and the same logo (just smaller). Consistency builds recognition.

Avoid Embedding Images as Base64

Base64-encoded images inflate your email size and are stripped by many mobile clients. Always host images on a CDN or image hosting service and reference them with standard <img> tags using HTTPS URLs.

Consider a Centralized Signature Management Tool

Managing separate signatures across desktop Outlook, desktop Gmail, iOS Mail, the Gmail app, and the Outlook app is tedious and error-prone. Centralized platforms like Signkit let you design one signature that deploys correctly across every client and device. This is especially valuable for teams where brand consistency matters across dozens or hundreds of employees.

Browse our signature template library to see mobile-optimized designs you can deploy in minutes.

How to Test Your Mobile Email Signature

Testing is the most important step that most people skip. Here is a practical testing process.

Step 1: Send Test Emails

Compose a short test email with your new signature and send it to:

• Your own email address (to check the sender's view)
• A Gmail account
• An Outlook/Hotmail account
• An iCloud or Apple Mail account

Step 2: Open on Multiple Devices

Check each test email on:

• Your phone's default mail app
• The Gmail app
• The Outlook app
• A desktop browser (to see how it renders there too)

Step 3: Check These Specific Things

• Do images load correctly? Are they the right size?
• Is text readable without zooming?
• Can you tap phone numbers and links easily?
• Does the signature fit within the screen width without horizontal scrolling?
• Is the signature proportionate to a short reply (two to three lines of text)?

Step 4: Test in Dark Mode

Many mobile users have dark mode enabled. Check that your signature:

• Does not use transparent PNGs on text that becomes invisible on dark backgrounds
• Has sufficient contrast between text and background
• Uses images with non-transparent backgrounds or adapts to dark mode

Frequently Asked Questions

How do I add an HTML email signature on my iPhone?

You cannot create HTML signatures directly in the iOS Mail signature editor. Instead, design your signature on a desktop computer or use a signature generator tool. Send yourself an email containing only the signature, open it on your iPhone, select all the content, copy it, then paste it into Settings > Mail > Signature. This preserves images and formatting that the plain text editor does not support natively.

Why does my email signature look different on mobile than on desktop?

Mobile email clients use different rendering engines and strip certain CSS properties. Gmail's mobile app is particularly aggressive, removing embedded stylesheets and some inline styles. Additionally, the narrower screen width (320 to 428 pixels vs. 1200+ pixels on desktop) forces content to reflow. Using inline CSS, single-column layouts, and images under 320px wide minimizes these differences.

Can I have a different signature for mobile and desktop?

Yes, most email apps maintain separate signature settings for mobile and desktop. Your Gmail mobile app signature is independent of your Gmail desktop signature. Your Outlook mobile signature is separate from Outlook desktop. You can use this to set a simpler, shorter signature on mobile while keeping a fuller version on desktop. The downside is that you must manage both versions separately.

What is the ideal image size for a mobile email signature?

Keep all images under 320 pixels wide to ensure they display correctly on the smallest common mobile screens. Logos work best at 100 to 200 pixels wide. Headshot photos should be 80 to 100 pixels square. Social media icons should be 20 to 24 pixels each. For file size, keep individual images under 50KB and the total signature under 100KB to ensure fast loading on mobile data connections.

How do I manage email signatures across my entire team's mobile devices?

Managing individual signatures on dozens or hundreds of phones is impractical. Server-side signature solutions through Google Workspace or Microsoft 365 can inject signatures at the mail server level, overriding whatever is set on the device. Alternatively, a dedicated email signature management platform like Signkit lets administrators design, deploy, and update signatures centrally across all employees and devices without touching individual phones.

Key Takeaways

• Set up mobile signatures separately from desktop because no major email app syncs signatures between mobile and desktop clients automatically, and each requires its own configuration.
• Keep images under 320px wide and total signature size under 100KB to prevent broken layouts and slow loading on mobile screens and cellular connections.
• Use single-column, table-based HTML with inline CSS as the only reliable way to ensure your signature renders consistently across iOS Mail, Gmail, Outlook, and Samsung Email.
• Test on at least four devices and apps before deploying, including iPhone Mail, Gmail app, Outlook mobile, and a desktop client, to catch rendering issues before your recipients do.
• Consider centralized signature management for teams because manually maintaining separate signatures across every employee's desktop and mobile apps creates inconsistency and wastes time that a platform like Signkit eliminates.

Take Control of Your Mobile Email Signature

Setting up a mobile email signature does not have to be a frustrating, trial-and-error process. Whether you are configuring a single phone or rolling out signatures across an entire organization, the principles are the same: keep it simple, keep it under 320px wide, use inline styles, and test thoroughly.

If you are tired of managing separate signatures for every device, client, and employee, Signkit gives you one place to design, deploy, and update email signatures that look right everywhere. Start with our free signature templates and see the difference a well-managed signature makes.