Tokenization stores sensitive payment details remotely using a payment gateway processor. WHMCS supports many tokenized payment gateways.
Affiliate links include unique codes to set cookies and track the referrals that originate from each of your affiliates in WHMCS.
Client groups allow you to categorize your clients. You can use client groups to set domain pricing slabs, apply discounts, and more.
If a module for your payment gateway doesn't exist yet, you can develop your own custom payment gateway modules using the examples here.
Email importing retrieves customers' email replies to support tickets. You can use POP3, IMAP, Google®, or Microsoft® for email importing.
Email piping automatically imports email replies that a support department email address receives into the corresponding support ticket.
After invoice generation, you can easily manage your clients' invoices, including payment, splitting invoices, cancelling them, and more.