macOS 27 Golden Gate: Apple Mail Signature Missing or Broken? Here's the Fix
You upgraded to macOS 27 and your Apple Mail signature is missing, empty, or no longer attached to your account. It is almost certainly still on your Mac. Here is where it went, and the order to check.
Step by step
Check All Signatures before you rebuild anything
Mail → Settings → Signatures, then select All Signatures in the left column. An upgrade usually unassigns signatures rather than deleting them. If yours are listed, drag each one back onto its account and you're done — no recovery needed.
Check the account, not just the list
If an account was re-provisioned during the macOS 27 upgrade — common with iCloud and Exchange — it comes back with no signature assigned. Select the account in the left column and re-assign, then set Choose Signature at the bottom.
Confirm iCloud Drive → Mail is still on
System Settings → your name → iCloud → iCloud Drive → Apps syncing to iCloud Drive. If the upgrade flipped Mail off, your synced signatures are hidden, not deleted — switching it back on restores them within a few minutes.
Look in the folder the upgrade left behind
macOS versions Mail's data folder, and an upgrade can leave the old one in place as a dead copy. With iCloud Drive Mail on, look in ~/Library/Mobile Documents/com~apple~mail/Data/V4/Signatures/; with it off, ~/Library/Mail/V10/MailData/Signatures/. Check the older V folders too — that's usually where the content still is.
Recover the content by hand
Open the .mailsignature files from that folder in TextEdit. Past the few header lines, the body of your signature is plain HTML. Create a fresh signature in Mail and paste the content back in.
Time Machine, if it comes to that
Enter Time Machine, browse to the signatures folder above at a date before the upgrade, and restore it. Quit Mail first, or Mail will overwrite what you restore.
What the upgrade actually does
The good news first: on the Mac we upgraded, the signature came through the upgrade intact. It stayed in the list, it stayed assigned to its account, its formatting and images survived, and iCloud sync kept working — the signature was still present and correct on the other Macs on the same account. On this machine macOS 27 did not touch signatures at all.
That is worth saying plainly, because the searches that bring people to this page spike every September whether or not anything is actually broken. If yours is fine, nothing below needs doing.
If yours did not survive, that is still worth working through rather than rebuilding from scratch — a clean upgrade on one Mac does not mean every configuration is clean. The two situations that still bite are an account that gets re-provisioned during the upgrade (it comes back with no signature assigned) and a second Mac on the same iCloud account overwriting the synced set. The steps above cover both, in the order most likely to work.
The reason this recurs every September is structural, and it’s worth understanding once. Apple Mail keeps signatures in two mutually exclusive locations, decided by a single switch:
- iCloud Drive “Mail” ON (the default) —
~/Library/Mobile Documents/com~apple~mail/Data/V4/Signatures/. With this on,~/Library/Mailis never created at all. - iCloud Drive “Mail” OFF —
~/Library/Mail/V10/MailData/Signatures/.
And a signature isn’t one file. It’s three things that don’t travel together: the catalog
(AllSignatures.plist — syncs), the content (<UUID>.mailsignature — syncs),
and the account binding, which does not sync because it points at account IDs unique to each Mac. An upgrade
that migrates the data folder can carry two of those three across, which is exactly what an empty or unassigned
signature looks like from the outside.
Never rebuild a signature again
Autograph keeps your signature in its own library, outside Mail’s data folder. After any macOS upgrade, reinstalling it is one click — and Autograph repairs the assignment for you.
Download for Mac More guidesCommon questions
Does macOS 27 delete Apple Mail signatures?
Usually not. In the overwhelming majority of reports the signature is still on disk — the upgrade broke the assignment between the signature and the mail account, or moved the data folder and left Mail reading a different one. Work through the steps above before rebuilding anything.
There is no ~/Library/Mail folder on my Mac. Where are my signatures?
That folder only exists if iCloud Drive Mail is switched off. With it on — the default — macOS never creates ~/Library/Mail at all, and your signatures live in ~/Library/Mobile Documents/com~apple~mail/Data/V4/Signatures/ instead. This is why most published fixes dead-end: they assume the local folder.
My signature came back empty — the name is there but nothing is in it.
Mail stores the catalog (AllSignatures.plist, the names you see) separately from the content (<UUID>.mailsignature, the actual HTML). Both sync via iCloud, but not always together. An empty signature means the catalog arrived and the content didn't — recover it from the old folder, or from another Mac that still has it.
Should I have waited to upgrade to macOS 27?
It wouldn't have helped for long. This has happened across Sonoma, Sequoia, and Tahoe — the signature store gets migrated on every major upgrade. The durable fix is keeping your signature somewhere outside Mail's data folder so it can be reinstalled in one click, which is the problem Autograph exists to solve.