Posted on 30 July 2026

How to create an email signature in Outlook (and why yours keeps breaking)

Outlook has a signature editor built in, and for a few lines of plain text it is perfectly good. Type your name, add your job title, done. Where it starts to struggle is the moment you want something that looks designed — a logo, a set spacing, a layout that survives being replied to.

This is the honest version of the instructions: whether your signature follows you between devices, where the settings actually live in each version of Outlook, and then the three things that go wrong afterwards, which nobody warns you about until it has already happened in front of a client.

Whether your signature follows you between devices

This used to be simple to answer, and the answer used to be no. Microsoft ships several different products all called Outlook, and for years none of them shared signatures with any of the others. Set one up on your laptop and it would not appear in the browser, or on your phone, or in the new Outlook if you switched.

That changed with a feature Microsoft calls roaming signatures, and it is worth understanding before you start, because it decides whether you are setting your signature up once or five times. Roaming signatures store the signature in your mailbox rather than on your computer, so it travels with the account.

It does not apply to everyone. You get it if your mailbox is on Microsoft 365 or Outlook.com, and you are running Outlook build 2303 or later. You do not get it on an on-premises Exchange server, or a POP or IMAP account, or a third-party mail provider — those still keep signatures on the individual machine. It is also possible for an IT administrator to switch the whole thing off, and some third-party signature management tools deliberately do exactly that, so in a managed company setup it may well be disabled without anyone mentioning it.

Where it gets genuinely annoying is the coverage. Microsoft’s own documentation says a roaming signature will be available on “all devices where that account is configured”, which is not true, and Microsoft’s support staff have acknowledged as much. In practice it works between classic Outlook for Windows, the new Outlook for Windows, and Outlook on the web. It does not reach Outlook for Mac, and it does not reach the iPhone and Android apps at all.

So the short version: if you are on Microsoft 365 or Outlook.com and you work on Windows and in a browser, set it up once. If a Mac or a phone is involved, you are still setting it up again there by hand. And if your mail is on an old Exchange server or an IMAP account, nothing has changed and every device is its own job.

One side effect worth knowing about. When the feature arrived, Outlook copied across only the signatures you had set as the default for new messages or for replies. Anything else stayed behind on the machine, and you will now see it in a separate group called Signatures on this device. If a signature you swear you created has gone missing, look there before rebuilding it.

Where Outlook keeps its signature settings

Classic Outlook for Windows

Go to File → Options → Mail, then click Signatures. You can also get to the same dialog from a new email, via Message → Signature → Signatures, which is the route Microsoft’s own instructions take.

Under Select signature to edit, choose New, give it a name, and build it in the box below. Before you close the window, look at Choose default signature on the right and set the dropdowns for New messages and Replies/forwards. These are set per email account, so if you have two accounts you need to do it twice. On a Microsoft 365 or Outlook.com mailbox that same dropdown will also list Signatures on this device, which is the local-only group described above.

New Outlook for Windows

Click the Settings gear in the top right, then Accounts → Signatures. Click Add signature, name it, and build it. The defaults here are checkboxes at the bottom of the editor rather than dropdowns, so tick the one for new messages before you save.

Outlook for Mac

Open the Outlook menu and choose Settings, then under Email select Signatures. Settings opens as a grid of categories rather than a list, which is why that middle step matters. The usual macOS Cmd + , shortcut opens the same window.

There are currently two different Mac apps in circulation. If your Settings look nothing like the above, you are probably in the older one, where the path is Outlook → Preferences → Signatures. Microsoft has said support for legacy Outlook for Mac ends in October 2026, so that route is on its way out.

Outlook on the web, and Outlook.com

Open Settings, then Accounts → Signatures. If your account does not show that, look under Mail → Compose and reply instead, which is where it used to live. Microsoft’s own help pages currently describe both locations, and label the button either Add signature or + New signature, so it is worth checking both rather than assuming yours is broken.

Outlook on iPhone and Android

Tap your profile picture in the top left, then the settings gear, then under Mail tap Signature. The gear is not on the main mail view, which is why this one is so often reported as missing. If you have more than one account on the phone, there is a Per Account Signature toggle here that decides whether they share one signature or get their own.

In practice the mobile apps are where designed signatures come unstuck. Images and complex HTML frequently fail to survive the trip from a desktop signature, which is why most people end up settling for their name and phone number here.

Three things that break Outlook signatures

Once the signature is in place, three problems show up in roughly this order. All three are worth understanding whether or not you ever use a tool for this.

1. Your logo arrives as an attachment

This is the big one. When you insert a picture into an Outlook signature, Outlook embeds the image file in every message you send. The recipient sees a paperclip on a one-line email asking what time the meeting is, and after a while people start assuming your emails contain something important when they do not.

The fix is to stop embedding the file and reference the image by URL instead, so the signature points at a copy hosted on the web rather than carrying one. You can do this yourself if you have somewhere reliable to host an image: upload the logo, get its address, and use that address in the signature’s HTML. The two things to watch are that the URL has to stay alive forever, and it needs to be served over HTTPS or some mail clients will refuse to load it.

2. The layout falls apart on replies

A signature that looks right in a new message often collapses once it is three replies deep, or once it reaches somebody reading it in Gmail. Email clients each rewrite HTML in their own way, and the more structure your signature depends on, the more there is to rewrite.

Keeping it simple genuinely helps. Avoid deeply nested tables, do not rely on background images, set your spacing explicitly rather than trusting the defaults, and give every image a fixed width. If it looks fine after you have replied to yourself twice, it will probably survive in the wild.

3. Editing the HTML directly is getting harder

Classic Outlook for Windows keeps each signature as three files on your machine — an .htm, an .rtf and a .txt, named after the signature, in %AppData%MicrosoftSignatures. You can open the .htm in Notepad and edit the HTML by hand, which is the classic way to get a properly built signature into Outlook.

Two warnings. It is worth fully quitting Outlook before you edit the file, so that nothing overwrites your changes while you work. More importantly, on a Microsoft 365 or Outlook.com mailbox with roaming signatures switched on, the signature lives in the mailbox rather than in that folder, and a hand-edit to the local file can simply be replaced the next time the account syncs. The local-file trick is now reliable mainly on on-premises Exchange, POP and IMAP accounts, or where roaming has been turned off.

The new Outlook for Windows is more restrictive again. Microsoft documents no signature file location and no HTML source view for it, so there is nothing to open in Notepad. The practical route in is to paste a finished, rendered signature into the editor and check what survives. Pasting from a browser works better than pasting from a document, and Chrome, Edge or Firefox are more reliable than Safari, which quietly alters formatting on the way through.

So should you just use Outlook’s own editor?

If your signature is a few lines of text, yes. Genuinely. It takes two minutes, it costs nothing, and none of the three problems above will trouble you, because they are all consequences of wanting something designed.

If you want a logo that does not attach itself to every message, a layout that holds together across mail clients, and the same signature on your laptop and your phone, then you are asking Outlook’s editor to do a job it was not built for. That is the point at which a signature generator earns its keep — it writes the HTML, hosts the images, and gives you something to paste into each version of Outlook. Designing one in Mirosign is free, so you can see whether the result is better than what you have before deciding anything.

Whichever route you take, there are step-by-step guides for getting a finished signature into classic Outlook for Windows, the new Outlook for Windows, Outlook for Mac, Outlook on the web, iPhone and Android.

Common questions

The questions below come up most often, and the answers depend more on which Outlook and which mailbox you have than most guides admit.

Why does my Outlook signature look different on replies?

Because each email client rewrites the signature’s HTML in its own way, and quoted reply chains add another layer of formatting on top. Simplifying the structure helps: fewer nested tables, explicit spacing, fixed image widths, and no background images.

Can I use HTML in an Outlook signature?

In classic Outlook for Windows, yes. Signatures are stored as .htm files in %AppData%MicrosoftSignatures and you can edit them directly, though on a Microsoft 365 or Outlook.com mailbox with roaming signatures enabled your edit may be overwritten by the next sync. In the new Outlook, Outlook for Mac and the web version there is no HTML editor, so you paste a rendered signature in instead.

Do I need to set up my signature again in the new Outlook?

Usually not. If your mailbox is on Microsoft 365 or Outlook.com and you are on Outlook build 2303 or later, signatures roam between classic Outlook for Windows, the new Outlook and Outlook on the web. On an on-premises Exchange, POP or IMAP account, or if your administrator has disabled roaming signatures, you do need to set it up again.

Why does my signature not appear on my phone?

Because roaming signatures do not extend to the Outlook apps for iPhone and Android, or to Outlook for Mac, despite Microsoft’s documentation implying they reach every device. You have to set the signature up separately in the mobile app, and images and complex formatting often will not survive being pasted in.

Why is my logo sent as an attachment?

Because inserting a picture into an Outlook signature embeds the image file itself in every message. To stop it, the signature needs to reference the image by URL from a reliably hosted copy served over HTTPS, rather than carrying the file.

Where does Outlook store signatures?

Classic Outlook for Windows stores each one as .htm, .rtf and .txt files in %AppData%MicrosoftSignatures. On Microsoft 365 and Outlook.com mailboxes with roaming signatures the signature is stored in the mailbox instead, and only local-only ones remain in that folder, grouped under “Signatures on this device”.