Troubleshooting16 min read

New Outlook Signature Problems: Every Known Issue and Fix (2026)

Microsoft’s “New Outlook for Windows” has been rolling out since late 2024, and it has broken email signatures for millions of users. If you’re here because your signature disappeared, looks wrong, won’t save, or just behaves completely differently than it did in Classic Outlook — you’re not alone, and this guide covers every known issue with a concrete fix for each one.

By the NeatStamp Team · Updated March 2026 · 16 min read

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What is “New Outlook” and why is Microsoft pushing it?

New Outlook for Windows is Microsoft’s replacement for the classic Outlook desktop application that most of us have used since the early 2000s. The old app was a native Windows application that rendered email using the Microsoft Word rendering engine. It was clunky, had an ancient HTML renderer, and was expensive to maintain.

New Outlook is built on a completely different foundation. It’s essentially an Electron-based wrapper around the Outlook Web App (OWA) — the same interface you see when you log into Outlook.com or outlook.office.com in a browser. The rendering engine underneath is Chromium, which is the same engine that powers Chrome, Edge, and most modern browsers.

For most things, this is an improvement. But for email signatures, it has caused significant breakage for three reasons:

  • Signatures are no longer stored locally as files. They live in the cloud via Microsoft 365, which means they don't automatically migrate from the old app.
  • The rendering engine is completely different. HTML and CSS that was specifically crafted to work around Classic Outlook's Word engine now behaves differently — sometimes better, sometimes worse.
  • Features that relied on Word-specific HTML extensions (like VML for shapes and rounded corners) simply don't work at all.

Microsoft started rolling out New Outlook as opt-in in late 2023, with a toggle switch in the top-right corner of Classic Outlook. By late 2024 it became the default for new installations. By 2025, Microsoft began removing the toggle for some Microsoft 365 Personal and Home subscribers, making the migration mandatory for those users.

The business and enterprise timeline is more extended — Microsoft has committed to keeping Classic Outlook available for commercial customers until at least 2026, with a full deprecation announcement expected. But for many home and small business users, the migration is already happening whether they chose it or not. And the first casualty is almost always the email signature.

The May 2025 incident that wiped signatures for thousands of companies

In May 2025, a Windows Update caused New Outlook to lose signature assignments for a large number of users. This wasn’t a small edge case — forums, Reddit threads, and IT helpdesks lit up with complaints from people who suddenly noticed their emails were going out with no signature.

What actually happened

The signatures themselves weren’t deleted. The cloud storage that holds the signature content was fine. What broke was the assignment— the setting that links an email account to a specific signature for new messages and replies. After the update, that link was cleared, and New Outlook fell back to “no signature” as the default.

The fix was simple — go to Settings → Accounts → Signatures and reassign the signature. But the damage was done. Many users (and their companies) sent emails without signatures for hours or days before anyone noticed. For sales teams, executives, and anyone where the signature carries legal disclaimers, this was a real problem.

If you’re managing signatures for a team, this incident is exactly why relying on individual users to set up and maintain their own signatures is risky. The company-wide signature management guide covers how to set up signatures centrally so one Windows Update can’t wipe everyone’s at once.

The incident also highlighted a deeper issue: New Outlook signature settings are not robust in the way Classic Outlook’s file-based system was. Local files don’t get wiped by cloud sync bugs. Cloud-stored settings can. Until Microsoft matures the New Outlook signature storage, you should treat your signature as something that might need to be reassigned after major updates.

All 12 known signature problems in New Outlook — and how to fix each one

1

Signatures didn’t migrate from Classic Outlook

Very common

This is the first thing people hit. You switch to New Outlook and your carefully crafted signature is just gone. No error, no warning — it simply doesn’t appear. That’s because New Outlook and Classic Outlook use completely different signature storage systems. Classic Outlook stored signatures as .htm, .rtf, and .txt files in %APPDATA%\Microsoft\Signatures. New Outlook doesn’t read that folder at all.

Fix

Manual re-setup is unavoidable. In New Outlook, go to Settings (gear icon) → Accounts → Signatures → New signature. If you still have access to Classic Outlook, you can open your signature there, copy the content, and paste it into the New Outlook editor. Or rebuild it from scratch using the NeatStamp editor, which generates HTML that works in both versions.

2

Only 1 signature per account (vs. unlimited in Classic)

Ongoing limitation

In Classic Outlook, you could create unlimited signatures and assign different ones for new messages, replies, different accounts, or switch manually while composing. Sales reps would use different signatures for different contexts. Executives had a formal version and a casual version. New Outlook cuts this down to one signature for new messages and one for replies — per account.

Workaround

There is no clean fix as of March 2026. Microsoft has acknowledged this on the Microsoft 365 roadmap as a feature request with significant votes. The practical workaround is to keep one all-purpose signature and manually edit it when you need a different variant. Alternatively, some teams use OWA (Outlook Web Access) which has slightly more flexibility. If your team needs multiple signature variants, this alone may be reason to delay migration to New Outlook.

3

HTML formatting looks different (web engine vs. Word engine)

Very common

Classic Outlook used the Word rendering engine — the same engine that renders Word documents. It had notoriously bad CSS support: no flexbox, no grid, limited border-radius, no CSS variables, partial margin support. Signature HTML for Classic Outlook was written defensively, with table-based layouts and inline styles specifically to work around these limitations.

New Outlook uses a Chromium-based engine. It supports modern CSS. This sounds like an improvement — and it often is — but it means your Classic-Outlook-optimized signature HTML may now render differently. Tables that were sized to compensate for Word’s quirks can look off in Chromium. Spacing that was tuned for Word’s odd margin interpretation may now have too much or too little whitespace.

Fix

Test your signature in both versions side by side. The safest HTML uses table-based layout with inline CSS, with no VML and no conditional comments. This renders predictably in both the Word engine and the Chromium engine. See the Outlook-compatible HTML guide for the full ruleset. The compatibility checklist lists every property to avoid.

4

Images appear larger or distorted

Common

Your company logo or headshot looks fine in Classic Outlook but blows up to an enormous size in New Outlook — or vice versa. The cause is almost always missing width and height attributes on the <img> tag, combined with the difference in how the two rendering engines handle unsized images.

Classic Outlook’s Word engine would sometimes apply default sizing constraints to images. Chromium in New Outlook renders images at their native pixel dimensions unless explicitly constrained. So a 600px-wide logo that looked fine because Word was compressing it now fills the entire screen.

Fix

Add explicit width and height attributes to every image tag in your signature HTML. Use the actual display size you want, not the image’s native size. Also add style="width:Xpx;height:Ypx;" as an inline style as a belt-and-suspenders approach, since some clients ignore HTML attributes in favor of CSS. Use images that are 2x the display size for retina screens, but constrain them to the display size via attributes.

5

Fonts render differently (Calibri Light missing, etc.)

Common

Several users have reported that fonts like Calibri Light either don’t render at all or look different in New Outlook. Some fonts that were available via Windows font substitution in Classic Outlook aren’t available in the Electron/Chromium environment. Other fonts render at slightly different weights or metrics due to the engine change.

Fix

Stick to system-safe fonts for email signatures: Arial, Verdana, Georgia, Trebuchet MS, Tahoma, Times New Roman, and the standard Calibri (not Calibri Light). Always specify a fallback stack in your font-family declaration, like font-family: Arial, Helvetica, sans-serif. Web fonts (Google Fonts, etc.) are unreliable in email clients and should be avoided entirely.

6

Signature won’t save (known bug with OWA workaround)

Known bug

Some users get stuck in a loop where they type or paste a signature, click Save, and nothing happens — or the signature appears to save but disappears the next time they open settings. This happens most often when the signature HTML contains characters or elements that the New Outlook save function doesn’t handle correctly, particularly complex formatting or certain special characters.

Workaround

Use OWA (Outlook Web App) instead of the desktop app to set up your signature. Go to outlook.office.com, log in with the same account, then go to Settings → Mail → Compose and reply → Email signature. Set up your signature there. Because New Outlook and OWA share the same cloud backend, the signature you set in OWA will appear in New Outlook. This bypasses whatever bug is preventing the save in the desktop app. See the related guide on Outlook signature not saving for more detail.

7

No access to the %APPDATA%\Signatures folder

By design

Classic Outlook stored signatures as files you could directly edit, back up, copy between machines, and version-control. The folder at %APPDATA%\Microsoft\Signatures contained .htm, .rtf, and .txt versions of each signature. Many IT departments used scripts to deploy signatures by simply writing files to this folder. New Outlook doesn’t use this folder at all.

What this means

Signatures in New Outlook are cloud-stored via Microsoft 365. This means file-based deployment scripts won’t work. IT teams need to use the Microsoft 365 admin center, PowerShell with Exchange Online cmdlets, or a third-party signature management platform to deploy signatures centrally. If you relied on the Signatures folder for backup or portability, that workflow no longer applies. See company-wide Outlook signature management for modern alternatives.

8

Roaming signatures conflict

Common for Microsoft 365 users

Microsoft 365 introduced “roaming signatures” — a feature that syncs signatures across devices via the cloud. This should be convenient, but it creates conflicts when users have set up different signatures on different devices and the sync overwrites the preferred version. It also interacts oddly with signatures set up in OWA vs. in the desktop app.

For a full breakdown of how roaming signatures work and what goes wrong, the Outlook roaming signatures guide covers every edge case in detail.

Fix

If roaming signatures are causing conflicts, you can disable the feature via the Microsoft 365 admin center (Exchange admin center → Org settings → Roaming signatures). If you’re an individual user without admin access, the cleanest approach is to delete all signatures across all devices and OWA, then set up fresh in one place and let it sync.

9

VML code is ignored

Breaking change

VML (Vector Markup Language) is a Microsoft-specific HTML extension that Classic Outlook supported for drawing shapes, applying background images to table cells, and creating rounded corners. Many professional email signature templates — especially older ones or those built specifically for Outlook — rely on VML for visual effects that couldn’t be done with standard CSS in the Word renderer.

In New Outlook, VML is completely ignored. Not rendered incorrectly — just not rendered at all. If your signature has a colored background panel achieved via VML, it will be gone. If you have a circular headshot using VML for the mask, it will be a plain square image or nothing.

Fix

Replace VML elements with their CSS or standard HTML equivalents. For background colors on table cells, use bgcolor attribute and background-color inline style. For rounded corners, use border-radius (which New Outlook’s Chromium engine supports, even though Classic Outlook didn’t). For background images, note that New Outlook supports CSS background-image on table cells — something Classic Outlook required VML for. Rebuild any VML-dependent design elements from scratch.

10

Conditional comments are stripped

Breaking change

Classic Outlook conditional comments look like this:

<!--[if mso]> <table width="600"> <!-- Classic Outlook-specific layout --> </table> <![endif]-->

These were a way to send Classic Outlook-specific HTML that other clients would ignore, because those clients would just see it as an HTML comment. Many signature templates used conditional comments extensively — wrapping VML in conditional comments, applying different table widths, adding Outlook-specific spacing.

New Outlook strips conditional comment blocks entirely. The entire block between <!--[if mso]> and <![endif]--> is removed. If your signature used conditional comments to show elements that Classic Outlook needed, those elements won’t appear at all.

Fix

Audit your signature HTML for any conditional comment blocks and replace them with standard HTML that works in both renderers. The goal is a single HTML structure that renders well in both Classic Outlook’s Word engine and New Outlook’s Chromium engine — which is possible if you stick to table-based layouts and inline CSS. Read more in the Outlook-compatible signature guide.

11

Signature resets after New Outlook updates

Intermittent bug

This is the signature-assignment bug that caused the May 2025 incident (see above), but it also happens at a smaller scale with routine New Outlook app updates. After an update, New Outlook may clear the assignment that links your email account to a specific signature. The signature still exists in storage, but the setting saying “use this signature for new messages” gets cleared.

Workaround

After any significant New Outlook update, check your signature settings before sending email. Go to Settings → Accounts → Signatures and verify that your signature is still assigned to the correct account for both new messages and replies. It takes 30 seconds and prevents the embarrassment of sending emails with no signature. Microsoft is aware of this bug; watch the update notes for a fix.

12

Can’t edit HTML source directly

By design

Classic Outlook had a workaround for editing signature HTML: you could open the .htm file in the Signatures folder directly in Notepad or a code editor. You could tweak anything. New Outlook doesn’t expose an HTML source editor anywhere in the UI, and the signature content lives in the cloud, not in accessible local files.

If you paste HTML into the signature editor using the standard paste function, New Outlook’s editor will strip or modify your code — it tries to “clean up” HTML and often removes things you need.

Workaround

The most reliable method: use OWA to set up the signature. In OWA’s signature editor, you can paste rendered HTML (copy the rendered visual output from a signature tool, not raw code) and it preserves formatting better than the desktop editor. Alternatively, use the NeatStamp editor to build and preview your signature, then use the Install Guide specific to New Outlook — it walks through the exact paste method that preserves your formatting. The Outlook 365 signature guide covers this in detail.

How to check if you’re on New Outlook

The clearest indicator is a toggle switch in the top-right corner of the Outlook window. If you see a toggle labeled “New Outlook” or “Try the new Outlook” — and it’s switched on— you’re on New Outlook.

Other signs you’re on New Outlook:

  • The interface looks significantly different — cleaner, more web-like, similar to Outlook.com
  • File → Options no longer exists (New Outlook uses a Settings panel instead)
  • There is no more Word-like ribbon for composing email — the toolbar is simpler
  • You can't find the Signatures folder at %APPDATA%\Microsoft\Signatures, or it's empty
  • When you right-click the taskbar icon, it says 'Outlook' not 'Outlook (new)'

If you’re unsure, the definitive check is to look at Help → About in Classic Outlook — the version number and app name will confirm which one you’re running. New Outlook reports a version number in the format “1.2025.XXXX.X” while Classic Outlook reports “16.X.XXXXX.XXXXX”.

How to switch back to Classic Outlook (while you still can)

Time-sensitive

Microsoft is removing the ability to switch back for some user types. As of March 2026, Microsoft 365 Personal and Home subscribers on the Current Channel can no longer toggle back to Classic Outlook in some regions. If you still have the toggle, use it now if you need to — it may disappear after the next update.

If you currently see the New Outlook toggle and it’s turned on, you can switch back by clicking the toggle to turn it off. Outlook will restart in Classic mode. Your Classic Outlook signatures should still be intact in the Signatures folder (they’re not deleted when you switch to New Outlook).

If the toggle is gone and you’re stuck on New Outlook, there are two options:

Option 1: Use the classic Outlook installer

Microsoft still provides the classic Outlook .exe installer for Microsoft 365 Business, Enterprise, and Education subscribers. IT admins can deploy it via the Office Deployment Tool. Individual users can sometimes find it via their Microsoft 365 account portal under Apps & devices.

Option 2: Adapt to New Outlook

If you can't switch back, the practical path is to rebuild your signature to work correctly in New Outlook. Follow the dual-compatibility rules in the next section, use the NeatStamp editor which generates New Outlook-compatible HTML, and verify your signature looks right before sending.

Microsoft’s official end-of-life date for Classic Outlook is still subject to change, but internal communications suggest it will be fully deprecated by mid-2026 for most commercial customers and 2027 for Enterprise. If your organization relies heavily on Classic Outlook signature workflows, now is the time to plan the migration.

Making signatures that work in both Classic and New Outlook

The good news: it’s possible to write one signature that works correctly in both Classic and New Outlook. Your organization may have a mix of users on both versions, or you may want to future-proof your signature before the forced migration. Here are the rules.

Layout: table-based, always

Both Classic Outlook’s Word engine and New Outlook’s Chromium engine handle HTML tables reliably. Use <table>, <tr>, and <td> for your layout. No div-based layouts, no flexbox, no CSS grid. Tables are the one thing both engines agree on.

CSS: inline only, safe properties only

Safe to use

  • ✓ color
  • ✓ font-family
  • ✓ font-size
  • ✓ font-weight
  • ✓ font-style
  • ✓ text-align
  • ✓ text-decoration
  • ✓ padding
  • ✓ border (simple)
  • ✓ background-color
  • ✓ width (on td/table)
  • ✓ line-height

Avoid

  • ✗ display: flex
  • ✗ display: grid
  • ✗ position: absolute
  • ✗ VML elements
  • ✗ <!--[if mso]-->
  • ✗ border-radius (Classic breaks)
  • ✗ box-shadow
  • ✗ opacity
  • ✗ transform
  • ✗ CSS variables (--var)
  • ✗ Web fonts (@import)
  • ✗ external stylesheets

Images: hosted externally, sized explicitly

Host all images on a public HTTPS server. Do not use base64-encoded images. Do not use cid: references. Add explicit width and height attributes to every <img> tag. Mirror these in inline styles. This prevents the size distortion problem and keeps images from appearing as attachments.

No VML, no conditional comments

These are the two biggest breaking changes. Audit any existing signature HTML for VML tags (they start with v: like <v:rect>) and for conditional comment blocks. Remove or replace both with standard HTML equivalents.

Safe fonts with fallbacks

Stick to web-safe system fonts: Arial, Verdana, Georgia, Tahoma, Trebuchet MS, regular Calibri. Always specify a fallback like font-family: Arial, Helvetica, sans-serif. This ensures consistent rendering when the first-choice font isn’t available. For further guidance, see the Outlook signature HTML reference.

If you follow these rules, your signature will render consistently across both Classic Outlook (with its Word engine) and New Outlook (with its Chromium engine). It will also work correctly in Gmail, Apple Mail, Outlook mobile, and most other clients. The Outlook email signature setup guide walks through installation for both versions step by step.

How NeatStamp handles New Outlook compatibility

When Microsoft started rolling out New Outlook, we updated our signature generator to produce HTML that works correctly in both versions. Every signature you build in NeatStamp uses table-based layout with inline CSS, externally hosted images with explicit dimensions, safe system fonts, and no VML or conditional comments.

We also added a New Outlook Migration Checker that runs 15 compatibility tests against your signature HTML before export:

  • ✓No VML elements detected
  • ✓No conditional comments
  • ✓No base64 image data
  • ✓All images have width/height
  • ✓No external stylesheets
  • ✓No CSS flexbox or grid
  • ✓No web font imports
  • ✓All links use https://
  • ✓Images on public CDN
  • ✓No CSS variables
  • ✓No position: absolute
  • ✓Font-family fallbacks present
  • ✓No cid: image references
  • ✓Table layout confirmed
  • ✓Inline CSS only

If any check fails, NeatStamp tells you exactly what the problem is and how to fix it before you copy the signature into Outlook. This is the kind of thing that used to require a developer to audit — now it’s automated.

We also provide a New Outlook-specific install guide inside the editor, with the exact copy-paste method that preserves your formatting in the New Outlook signature editor. It’s one of the trickier parts of New Outlook setup and the guide saves significant trial and error.

Build a New Outlook-compatible signatureBrowse templates

Frequently asked questions

Why did my signature disappear when I switched to New Outlook?

New Outlook does not import signatures from Classic Outlook. They are completely separate systems. Classic Outlook stores signatures as local files in %APPDATA%\Microsoft\Signatures. New Outlook stores them in the cloud via Microsoft 365. You have to recreate every signature manually in the new interface.

Can I have multiple signatures in New Outlook?

As of early 2026, New Outlook only allows one signature per email account — one for new messages and one for replies. Classic Outlook had no limit. Microsoft has acknowledged this as a known limitation and has it on the roadmap, but there is no confirmed release date.

How do I edit the HTML source of my signature in New Outlook?

You cannot. New Outlook does not expose an HTML source editor. The only workaround is to compose a new email, paste your HTML signature into the body (using a tool that lets you paste raw HTML), then copy it and paste it into the signature field. It is clunky but it works. Alternatively, use NeatStamp to build the signature and copy the rendered output.

Why do my signature images look bigger or distorted in New Outlook?

New Outlook uses a Chromium-based rendering engine instead of the Word engine used by Classic Outlook. Images without explicit width and height attributes will be rendered at their natural pixel size, which is often larger than intended. Add width and height attributes to every img tag in your signature HTML.

Does VML work in New Outlook?

No. VML (Vector Markup Language) is ignored entirely by New Outlook. VML was used in Classic Outlook for rounded corners, background images, and shapes. In New Outlook, none of that renders. You need to replace VML elements with standard HTML and CSS alternatives.

Do Outlook conditional comments work in New Outlook?

No. Conditional comments like <!--[if mso]> are stripped by New Outlook's rendering engine. These were used to target Classic Outlook specifically. New Outlook treats them as invalid HTML and removes the entire block.

My signature keeps resetting after New Outlook updates. Why?

This is a known bug in New Outlook. After certain app updates, the signature assignment (which account uses which signature) gets cleared. The signature itself usually survives but it gets unassigned. Go to Settings → Accounts → Signatures and reassign it after each update until Microsoft patches this.

Can I switch back to Classic Outlook after Microsoft forces the migration?

Microsoft's timeline for removing the Classic Outlook toggle varies by license type. As of March 2026, most Microsoft 365 Personal and Home users can still switch back using the toggle in the top-right corner. Business and Enterprise users on certain plans have more time. Check the Microsoft 365 roadmap for your specific plan.

How do I make one signature that works in both Classic and New Outlook?

Use table-based layouts with inline CSS only. Avoid VML, avoid conditional comments, avoid CSS flexbox or grid, and use externally hosted images with explicit width and height. This subset of HTML renders correctly in both the Word engine (Classic Outlook) and the Chromium engine (New Outlook). NeatStamp generates this format by default.

What happened in May 2025 with New Outlook signatures?

A Windows Update pushed in May 2025 caused New Outlook to lose signature assignments for a large number of users. The signatures themselves were not deleted, but the setting linking each account to its signature was wiped. Affected users found that emails were going out with no signature. The fix was to go back into signature settings and reassign — but many users didn't know this and sent unsigned emails for days.

Fix your New Outlook signature today

NeatStamp generates signatures that pass all 15 New Outlook compatibility checks automatically. No VML, no conditional comments, no broken images. Just a signature that works — in New Outlook, Classic Outlook, and everywhere else.

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