Step 1:
Login to Your WHMCS Admin Panel. And Click on Setup> Email Template
Step 2:
Click On the "Create New Email Template" Button.
Choose Email Template Type "Product/Service", give a unique name, and click on "Create"
Step 3:
Type Subject, and in the body part including the major 3 fields
Step: 4
Click on "Save Changes"
To Apply a Welcome Email to your products/services.
Click on Setup> Products/Services > Products/Services
In Details Page Choose the Welcome Email Name from the dropdown list and finally click on "Save Changes"
Find below one example :
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Subject: Streaming Account Login Details: Important
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PLEASE READ THIS EMAIL IN FULL AND PRINT IT FOR YOUR RECORDS
Dear {$client_name},
Thank you for your order from us! Your video streaming reseller account has now been setup and this email contains all the information you will need in order to begin using your account.
New Account Information
Login URL: https://yourdomain.com/reseller/login
Username: {$service_username}
Password: {$service_password}
Thank you for choosing us.
{$signature