Outlook stores signatures in five different places depending on the version, and a working signature on one usually means a broken one on the others. Here's what's really happening, and how to fix it.
The MailSigCraft Team
MailSigCraft
If your Outlook signature isn't showing — or it shows on new emails but not replies, or only on desktop, or only when you compose from one of your three accounts — the cause almost always comes down to which Outlook you're actually using. Microsoft ships at least five products under the "Outlook" name, each with its own signature store, and they don't sync. A signature that works perfectly in classic Outlook for Windows will be invisible in the new Outlook for Windows, in Outlook on the web, on the iOS app, and on outlook.live.com.
This post walks through the nine specific reasons signatures vanish in Outlook, in rough order of how often we see each one. If you just want the clean install steps, the Outlook install guide covers the basics with screenshots.
For classic Outlook for Windows (the desktop client most companies still use):
That's it for the most common case. The remaining nine sections are everything that goes sideways from here.
Gmail has one signature store per account. Apple Mail has one per account. Outlook has five — and which one your client reads depends on the version, the account type (Microsoft 365 vs. Exchange vs. IMAP), and whether your IT admin has turned on roaming signatures. The five stores are:
%AppData%\Microsoft\Signaturesoutlook.office.com for Microsoft 365, outlook.live.com for personal) — cloud, separate from the new Outlook store on some tenantsSetting a signature in one of these does not propagate to the others unless your tenant has roaming signatures enabled and you're on a supported client. Half the "my signature disappeared" tickets we see are actually "I set it in classic Outlook, then opened the new Outlook, which has no signature configured because that's a separate store."
Microsoft has been migrating users from classic Outlook for Windows to the new Outlook for Windows for two years, and many people now have both installed without realising it. Open both, check File → Options → Mail → Signatures in the classic one and Settings (gear) → Accounts → Signatures in the new one. If you set a signature in classic and now compose in new (or vice versa), it won't show up.
The fix is to set it in both, or to commit to one client. We recommend setting it in whichever you actually use to send — and making sure your phone shortcut, taskbar pin, and mailto: handler all point at the same one.
In the Signatures dialog, the right-hand panel has two dropdowns: New messages and Replies/forwards. Outlook defaults the second one to (none) for new signatures, so your signature appears on first emails but not replies. Set both dropdowns to the same signature.
Above the dropdowns is an Email account selector. The signature configuration is per account — Outlook does not apply your signature to all accounts by default. If you have a personal Gmail, a work Microsoft 365 address, and an IMAP client account all configured in the same Outlook profile, you need to set the signature on each one.
This is also why people see signatures appear "randomly" — they appear on the account they configured and disappear on the one they didn't.
Outlook handles signature images differently from Gmail. If your signature uses externally-hosted images (URLs like https://cdn.example.com/logo.png), Outlook on the recipient side typically blocks them by default and shows a "Click here to download pictures" bar — or just a red X if image download fails entirely.
Two fixes:
Cache-Control and a permissive Access-Control-Allow-Origin, and that the URL is HTTPS. Outlook silently blocks http:// images on most modern builds.If your sender-side preview shows the image but the recipient sees a red X, it's almost always an external-image issue, not a signature configuration problem.
Classic Outlook for Windows renders HTML through Microsoft Word's rendering engine — not a browser engine. Word doesn't support flexbox, calc(), CSS variables, object-fit, or modern web fonts, and it scales fonts by your Windows display DPI rather than honouring CSS pixel sizes exactly.
The result: a signature designed in a browser-based editor looks 15–30% bigger in Outlook desktop than the designer intended, with extra vertical spacing where Word added margins. There's no fix from the user side once the signature exists; the only real solution is to design with Outlook's renderer in mind from the start. MailSigCraft templates are tested in classic Outlook for exactly this reason — table-based layouts, no flexbox, font sizes specified in pt rather than px, and explicit cellpadding=0 cellspacing=0 everywhere.
If your account or recipient has been forced into plain-text mode, the HTML signature is stripped and replaced with the plain-text version (which Outlook auto-generates from your HTML — usually badly). Check File → Options → Mail → Compose messages in this format and confirm it's set to HTML, not Plain Text.
Some Exchange transport rules also force plain-text for outbound mail to specific domains. If only one recipient sees a broken signature and everyone else sees it fine, this is probably why — and it's an admin-level setting, not something you can override.
Microsoft 365 has a feature called roaming signatures (a.k.a. cloud signatures) that syncs your signature across the new Outlook, Outlook on the web, and recent builds of classic Outlook for Windows. When the feature is on, your signature is stored on the server, not in %AppData%.
The catch: cloud signatures take a few minutes to propagate, and if you've made changes locally while offline, the cloud version may overwrite your local one on next sync. If your signature "reverted" without you doing anything, this is the most likely cause. Wait two minutes and re-open the Signatures dialog before re-applying.
Outlook for iOS and Android supports a signature, but it's plain-text only on most account types — same restriction as the Gmail mobile app. Whatever you set under Settings → Signature inside the mobile app is what gets appended to mobile-composed emails. The desktop HTML signature does not carry over.
If most of your email comes from your phone, the realistic options are: (a) use a plain-text signature on mobile and accept the inconsistency, or (b) compose branded emails only from desktop. Some Microsoft 365 tenants now support cloud signatures on iOS too (roll-out is account-dependent) — check your Settings → Signature screen for a "Use roaming signature" toggle.
If you're on Microsoft 365 or on-premises Exchange, your IT admin can configure a transport rule that strips outbound signatures and replaces them with a centrally-managed disclaimer or footer. This is the corporate equivalent of Google Workspace's "Append footer" feature. When it's on, your personal signature is silently overridden — sometimes appended below the admin one, sometimes replaced entirely.
There's nothing you can do from the user side. If you're the admin and you want personal signatures to work, either disable the transport rule or use a signature-management tool that integrates with Exchange (MailSigCraft's Team plan handles this case by deploying a single template across all your seats).
Send an email to yourself at a different address — ideally not Outlook to Outlook, since that bypasses some of the rendering quirks. Send it to a personal Gmail account, open the email on:
Three things to check:
Microsoft is in the middle of a multi-year migration from classic Outlook to the new Outlook, and the signature behaviour is changing on its own cadence. Roaming signatures rolled out unevenly through 2024–2025; the new Outlook for Mac signature store changed behaviour in late 2025. If your signature suddenly stops working without you changing anything, check the publishedAt date on this post — we update the steps as Microsoft ships new builds.
Full install guide with screenshots: mailsigcraft.com/install/outlook.