How-to guide
How to add a signature in Apple Mail
Apple Mail on the Mac supports rich signatures with images, multiple signatures per account, and automatic assignment. The settings pane is compact and easy to miss — here's the full walkthrough.
Before you start: you'll need your signature as an image. The email signature generator builds the footer content, and the signature mark itself comes out as a transparent PNG that drags straight into Mail — free, no account, and nothing you type leaves your browser.
How Apple Mail handles signatures
Apple Mail's signature system is genuinely capable — multiple signatures, per-account assignment, images, even automatic rotation — but nearly all of it hides in one small settings pane that many Mac users never open. Signatures live in Mail → Settings → Signatures, organized in three columns: accounts on the left, signatures in the middle, content on the right.
Two behaviors trip people up. First, a signature created under All Signatures is just a draft — it does nothing until you drag it onto a specific account in the left column. Second, Mail embeds images by literal drag-and-drop into the editing pane; there's no insert button, and the image goes in at its native size because Mail has no resize control. Size the PNG before you drag it in.
Because Mail signatures are stored per-Mac (synced via iCloud only between Macs signed into the same account, and never to iOS), plan on setting up your iPhone separately — the steps are in adding an email signature on iPhone.
Step by step
Open Mail's signature settings
In Mail, choose Mail → Settings (older macOS: Preferences) from the menu bar, then click the Signatures tab.
Pick the account
The left column lists your email accounts. Select the account the signature belongs to — signatures created under All Signatures must be dragged onto an account before they can be used.
Create the signature
Click +, name the signature, and type your details in the right-hand pane. Uncheck Always match my default message font if you want it to keep its own styling.
Add your signature image
Drag your transparent signature PNG from Finder directly into the signature editing pane. It embeds inline — size it before dragging (300–400px wide is typical) since Mail doesn't resize images.
Set it as default
Below the editor, use Choose Signature to pick which signature is added automatically to new messages from that account — or leave it on None and add signatures per-message from the compose window.
Troubleshooting
Signature doesn't appear on new messages
The account's Choose Signature dropdown (below the signature list) is set to None. Set it to your signature — or to At Random / In Sequential Order if you keep several.
Image is enormous in the signature pane
Mail inserts images at native pixel size. Resize the PNG to 300–400px wide first (Preview: Tools → Adjust Size), then re-drag it in.
Signature loses its font when sending
"Always match my default message font" is checked, which strips your styling at send time. Uncheck it in the Signatures pane to preserve the signature's own formatting.
Signatures missing on my other Mac
Signature sync requires iCloud Drive with Mail enabled on both Macs. System Settings → Apple ID → iCloud → iCloud Drive → confirm Mail is on, then give it a few minutes.
Best practices
- Create two signatures per account — full for new mail, name-only for replies — and switch via the Signature dropdown in the compose window.
- Drag the finished signature onto every account that should have it; accounts don't share signatures automatically.
- Send a test to an Outlook or Gmail address: Apple Mail composes very clean HTML, but the receiving client decides how inline images display.
- Keep a copy of your signature content in Notes — if you ever rebuild your Mac, Mail signatures are easy to lose and annoying to reconstruct.
Common questions
Why is my image signature arriving as an attachment?
Some receiving clients (especially older Outlook versions) display inline images as attachments — that's on the recipient's side, not yours. Keeping the image small and in PNG format minimizes it.
Do Apple Mail signatures sync to iPhone?
No — macOS Mail and iOS Mail keep separate signatures. Set up the iPhone version separately: see adding a signature on iPhone.
Can I use different signatures for work and personal accounts?
Yes. Create signatures under each account in the Signatures tab, then set a different default per account with Choose Signature.
Can Apple Mail add a signature only when I choose?
Yes — set Choose Signature to None for the account, and pick a signature manually from the dropdown in each compose window when you want one.
Why do recipients see my logo as an attachment called 'unknown.png'?
Some clients (notably older Outlook) treat all inline images as attachments. Naming the file meaningfully before dragging it in (signature.png) and keeping it small reduces the noise, but the recipient-side behavior can't be fully controlled.
Does Apple Mail support HTML signatures?
Not through the UI, but the signature files on disk (~/Library/Mail/V*/MailData/Signatures) are HTML and advanced users edit them directly. For most people, composing in the pane and unchecking the match-font box achieves everything needed.