Note: Make sure you are using either Google Chrome or Firefox during the installation process.
Create your email signature on NEWOLDSTAMP.com and follow these simple steps to install it into Airmail.
After you finish creating your email signature, click Save and Install button under the signature preview:
Or if you have saved your signature priorly, hover over your signature on the dashboard and click Use button.
Select option Other in the list of the email clients.
Scroll down the Signature Preview and Click the Download HTML file button, and save your HTML email signature file to your Mac.
Open the HTML file within Google Chrome or Mozilla Firefox.
Copy your email signature by pressing Cmd + A to Select All, then Cmd + C to copy.
Switch to Airmail 3 and from the toolbar, select Airmail 3 > Preferences.
Now that you're in Preferences, you should have a new window open and, by default, be on the Accounts tab. To the far right of your listed email account, you will see a small settings cog icon, click this.
A new window will open up and you will see a few new tabs across the top, select the Signature tab. Select your email account, then click the + icon to enter a name for your signature.
Click inside the blank text box below and press Cmd + V to paste your copied email signature. Click Save.
Voila! Your new email signature is now installed. Please test it out by composing a new email to make sure it looks correct.