Copy your provided Signature Key. This may have been emailed to you, or you can access it from your Email Signature Rescue account.
Click the plus icon at the top left of the installer app to add a new email signature.
Click on the Select your email client drop down box and choose Apple Mail.
Click on the Select your email account drop down box and choose the email account you would like your email signature installed into.
Click on the insert your signature key field and press Ctrl + V to paste your copied signature key. If the key is valid, a green tick will appear on the right side.
Our installer app will now install your email signature into Apple Mail for you. When you compose a new email, your email signature will appear.
Open your HTML email signature file in your web browser.
Press Cmd + A to select the entire email signature, then press Cmd + C to copy it.
IMPORTANT: Do not use your mouse to select the area, only use Cmd + A as you may miss out on grabbing some of the code.
Open Apple Mail and from the menu bar select Mail then Settings. Select the Signatures tab at the top of the window.
From the left side, select the email account that you want to add your signature to. Click the + icon at the bottom of the middle column and enter a name for your email signature. On the right side, uncheck the Always match my default message font box then click inside the text field above and press Cmd + V to paste your copied email signature.
Now that your signature is added, click into the black space in the middle column and your email signature should get set as default in the Choose Signature dropdown below.
Close out of your Mail settings and compose a new email. Your email signature will now automatically insert when composing an email within Apple Mail on macOS 15 Sequoia.