There are several reasons why using a custom domain is beneficial:
Branding: A custom domain reinforces your brand identity every time you send an email. Trustworthiness: Recipients are more likely to trust an email from a custom domain than from a generic one. Deliverability: Custom domains often have better deliverability rates because they are less likely to be marked as spam. Tracking and Analytics: You can better track opens, clicks, and other metrics with a custom domain.