Apple Mail
How to install your Mysignature in Apple Mail on macOS
- 1
Copy your signature HTML
Open your signature in the Mysignature dashboard and click Copy Signature. Keep this copied — you will paste it in step 6.
Mysignature edit page with the Copy Signature button highlighted - 2
Create a placeholder signature in Apple Mail
Open Apple Mail. Go to Mail > Settings (or Preferences on older macOS) and click the Signatures tab. Select your email account on the left, then click the plus (+) button to add a new signature. Name it anything, for example "My Signature".
Apple Mail Signatures tab showing a new blank signature being created - 3
Quit Apple Mail completely
This step is critical. Press Cmd+Q to quit Apple Mail fully. Apple Mail writes the signature file to disk when it quits — if you skip this, the file will not exist yet.
macOS dock with Apple Mail icon showing the quit option - 4
Open the Signatures folder in Finder
In Finder, press Cmd+Shift+G to open "Go to Folder". Type: ~/Library/Mail/ and press Enter. Open the highest-numbered version folder (e.g. V10), then open MailData, then Signatures. You will see one or more .mailsignature files.
Finder showing the ~/Library/Mail/V10/MailData/Signatures folder with .mailsignature files - 5
Open the newest .mailsignature file in TextEdit
Sort the files by Date Modified and right-click the most recently modified .mailsignature file. Select Open With > TextEdit. You will see the placeholder content Apple Mail wrote.
.mailsignature file open in TextEdit showing the placeholder HTML - 6
Replace the content with your signature HTML
Select all the content in the TextEdit file (Cmd+A), delete it, and paste your copied signature HTML (Cmd+V). Save the file (Cmd+S) and close TextEdit.
TextEdit showing the pasted signature HTML replacing the placeholder - 7
Lock the file to prevent Apple Mail overwriting it
In Finder, right-click the same .mailsignature file and select Get Info (or press Cmd+I). At the bottom of the info panel, check the Locked checkbox. This stops Apple Mail from resetting the file when it reopens.
Finder Get Info panel with the Locked checkbox highlighted and checked - 8
Reopen Apple Mail
Open Apple Mail again. Go to Settings > Signatures and select your signature. The Settings preview may look plain — this is a known Apple Mail display bug. Open a new compose window to see the signature in full. Set it as your default under "Choose Signature" at the bottom of the panel.
Apple Mail new compose window showing the fully formatted HTML signature