How do i add a signature to my custom domain email?

Hi benstorch,

The steps here are geared towards your issue and should help you get that signature added:

1. "In the Mail app  on your Mac, choose Mail > Settings, then click Signatures.
2. In the left column (account list), select the email account where you want to use the signature.
3. If All Signatures is selected when you create a signature, you need to drag the new signature to the desired email account before you can use it.
4. Click the Add button  below the middle column.
5. In the middle column (signature list), type a name for the signature. 
6. This name appears in the Signature pop-up menu when you write a message.
7. In the right column (the preview), do any of the following to create your signature:

• Edit your text: Click Edit in the menu bar to paste text, turn text into links and check spelling and grammar.
• Format your text: Click Format in the menu bar to change the font and colour, change text alignment and add lists.
• Add an image: Drag an image into the preview area.

If you want your signature to appear after the original text of messages you reply to or forward, deselect the “Place signature above quoted text” tickbox."

You can find these steps along with other information that may be helpful, here: Create and use email signatures in Mail on Mac – Apple Support

If you have followed the steps correctly and you still have the issue, let us know if you get any specific alerts or error messages when trying, as those may help us determine what might be causing the issue.

If you still have questions, reach out to Apple Support directly, as this may require closer guidance: Get Support

Cheers!