Allow users to configure a custom sending domain and email addresses for system-generated communications (e.g., invoices, quotes) instead of the default D-Tools Cloud address (cloud@d-tools.com). This ensures emails appear branded and trustworthy to recipients while aligning with company-specific sender identities. Support standard email authentication methods (SPF, DKIM, DMARC) to maintain deliverability and security. Alternatively could add existing email platforms as an integration (e.g. Brevo, Mailchimp, Constant Contact, etc).