Unfortunately, iCloud.com does not support HTML email signatures. Please only use this guide if you’re planning to add a text-based email signature.
Once you are ready to set up your email signature, log in to your iCloud.com account and open Mail.
Click the Settings (cog-like) icon and select Preferences.
Click on the Composing tab.
Select “Add a signature” and then type your signature text in the field provided, such as Name, Address, Phone Number or anything you want to be displayed in your email signature.
Click the Done button. You have now installed your iCloud email signature and you can start composing emails.
To disable the email signature function in iCloud, simply unselect “Add a Signature” from the Composing tab and click Done.