Within Teamwork Desk, you can set a custom domain for your customer portal.
You can then direct your customers to your custom domain to create a support ticket.
To set your custom domain, click your profile icon to the top right of the navigation bar and select Settings.
In the Settings area, go to the Customer Portal subsection and select General Settings from the left sidebar.
In the Basics section, you will have the option to set a custom domain.
Note: Make sure you create a CNAME record for your domain which points to your Teamwork domain. This is required to make your custom domain for your customer portal work.
For more information, see: Setting Up Your Customer Portal