Step-by-step instructions for adding an HTML email signature in Apple Mail on macOS and iOS, plus fixes for the formatting and image problems that trip everyone up.
The MailSigCraft Team
MailSigCraft
Apple Mail is the third client people ask us about most, after Gmail and Outlook — and it has its own quirk: there's no "paste HTML" box. You have to trick Mail into accepting a rich signature by pasting it into the right place in the right order. This guide covers macOS, iPhone, and iPad, plus the handful of things that break along the way.
Open Mail, then from the menu bar choose Mail → Settings (older versions: Preferences).
Pick the email account in the left column. If you create the signature under All Signatures, it won't be assignable to a specific account.
Click the + button to create a new signature and give it a name.
This is the most-missed step. Leaving it on strips your fonts and colors on every send. Uncheck it before pasting.
Select everything in the signature preview box and delete the placeholder text.
Use Edit → Paste (Cmd+V). The images and layout from MailSigCraft's Copy Signature action carry over rich.
At the bottom of the dialog, set Choose Signature to your new signature so it's applied to new mail automatically.
It's almost always the font checkbox from step 4. Uncheck it, then re-paste. See the "Common problems" section below if it still strips.
iOS Mail signatures are managed in Settings, not inside the Mail app.
Go to Settings → Apps → Mail (older iOS: Settings → Mail).
Scroll to Signature. Choose Per Account if you want different signatures for different mailboxes.
iOS strips most rich formatting from typed signatures. The reliable workaround: email the finished signature to yourself, open it in Mail, copy it from the email, then paste it into the Signature field.
Long-press in the signature box and choose plain Paste (NOT Paste and Match Style — that strips formatting). Rich formatting survives the round-trip far better than typing it.
This is the "Always match my default message font" checkbox from step 4 above.
Uncheck the box, then re-paste. If it still strips, quit Mail completely (Cmd+Q), reopen, and paste again — Mail caches the signature editor state and a relaunch clears it.
You pasted the HTML source instead of the rendered signature.
In MailSigCraft, use Copy Signature (not "Copy HTML") so the rich version lands on the clipboard, then paste.
Older macOS Mail versions only keep pasted images if the signature file is saved correctly.
Make sure you clicked away from the signature (so it commits) before quitting. If images keep dropping, host them on a CDN with absolute URLs instead of embedding — MailSigCraft does this for you. See the image-not-showing post for the hosting checklist.
Apple Mail renders at the image's native pixel size. A 200×200 logo intended for 50px display takes up the full 200×200.
Export logos at 2× the display size and set explicit width="" and height="" attributes on the <img> tag so they scale down crisply instead of looking oversized. For a 50px logo, that's a 100×100 source PNG with width="50" height="50".
Apple Mail on macOS respects dark mode in the composer. A signature designed against a white background can render with washed-out text and a glowing rectangle around the logo when the recipient is in dark mode.
Avoid pure-black text on transparent backgrounds; use a slightly off-black (rgba(0, 0, 0, 0.85)) and test in both appearances. The full breakdown is in the dark mode survival guide.
This trips up almost everyone who follows the macOS steps first. Apple Mail signatures aren't stored in iCloud as a shared setting the way your inbox or your calendar is. Each device keeps its own local signature file.
There's one partial exception: a plain text-only signature (no logo, no formatting) can carry over between devices if you're signed into the same Apple ID with Mail enabled in iCloud settings. The moment your signature includes an image or rich formatting — which is the whole point of building one in MailSigCraft — that sync doesn't apply. You have to repeat the paste in both the macOS and iOS/iPadOS sections above, once per device. There's no setting that turns this on; it's a hard limit of how Apple Mail stores signatures, and it hasn't changed across recent macOS and iOS releases.
iOS Mail's signature field re-applies its own default text attributes the instant you paste into it, which can strip styling brought in from elsewhere. This is a known iOS Mail behavior, not something specific to MailSigCraft-built signatures — it happens to any rich content pasted into that field. If it happens even after copying from an email you sent yourself, try shaking your iPhone right after the paste — this surfaces an "Undo Change Attributes" option that reverses the auto-reformatting and restores the pasted styling.
Not through Apple Mail's own settings — see the sync limitation above. The fastest reliable workflow is the one this guide describes: keep the finished signature in your MailSigCraft dashboard, and when you need it on a new device, copy it and follow the matching macOS or iOS steps above. It takes under a minute per device once you've done it the first time.
Yes, and it's the Per Account option referenced in step 2 of both the macOS and iOS/iPadOS sections above. On the Mac, select each account in the left column of the Signatures tab and build a separate signature for it. On iPhone or iPad, choose Per Account on the Signature screen and each of your mailboxes gets its own signature box. The one requirement people miss: both accounts have to be added inside Apple Mail itself for this to work. If your work inbox lives in the separate Gmail or Outlook app instead of Apple Mail, that account's signature is controlled by that app's own settings, not Apple Mail's Per Account switch.
Build it once in MailSigCraft, copy it to your clipboard, and paste it into each device. The same signature will render correctly across Mac, iPhone, and iPad — and in your recipients' inboxes too.