Yes, both Postmark and Kustomer offer a Free Trial.
Postmark is designed for Individuals, Freelancers, Medium Business and Small Business.
Kustomer is designed for Large Enterprises, Medium Business and Small Business.
The starting price of Kustomer begins at $29/User/Month, while pricing details for Postmark are unavailable.
Some top alternatives to Postmark includes SMTP, Campaigner and Moosend.
Some top alternatives to Kustomer includes Zendesk Support, Zoho Desk, Tidio Helpdesk, Zendesk Sell, Freshservice, Freshdesk, HelpDesk, SysAid, Jitbit Helpdesk, Desky, Salesforce Service Cloud, CRMdesk, Gorgias, Trakdesk, AzureDesk and BoldDesk.