Hi,
I want to create a Zoho Mail extension similar to Outlook’s OnSend add-in. The extension should:

1. Let the user select headers and footers from a taskpane while composing an email.

2. When the user clicks Send, the extension should:

   • Automatically insert the selected header and footer into the email body.

   • Also add related custom internet headers to the outgoing email.

Is this possible with Zoho Mail’s current extension platform?

• Can I intercept or modify the message before it’s sent from the compose window?

• Can I programmatically add internet headers to outgoing emails?

• Are there any APIs or extension types that support this?

I’ve looked at compose widgets and the Developer documentation but couldn’t find clear details about modifying email content or headers on send.

Thanks in advance for any guidance.