Login to your Salesforce org where the package is installed.
Check for Lookup between Secure EmailMessage and source object. If there is no lookup, create a lookup relationship between them.
Create a Button named as Send Secure Email on Contact(Source object).
Action Type:- Lightning Component
Height:- 450px
Lightning Component: cm_datatransfer:sendSecureEmailAura
Label: Send Secure Email
Add the Button to Source Object(Contact) Page Layout
Add Related List Secure EmailMessages to the Source Object(Contact) Page Layout.
Create Email Template:
Go to App launcher and search for Email template.
Click on New Template and create a template as demonstrated in the image below.
Create a Text field named as Reply To Email on the Source Object(Contact).
Custom Settings
Go to MultipleToAddressMapping in Custom Settings
Map the Email Fields present on the Source Object(Contact).
Go to Paubox Credentials in custom Settings and enter the credentials there as shown in the below image.
Go to Email Configuration under Custom Metadata Types.
Map the Fields with source Object as shown in the image below.
Congratulations! You have successfully installed the Application.