Final answer:
To resolve the deployment issue in Salesforce, create an Environment Variable to replace the email-to-case address for all Metadata Deployments, ensuring the correct email address is used in each environment.
Step-by-step explanation:
When facing problems deploying an integration with an email-to-case address from Dev1 to INT in Salesforce, the address may not be located in the INT org. The solution to this issue is to create an Environment Variable and replace the email-to-case address for all the Metadata Deployments. This means the missing email-to-case address is specified as an environment-specific value, which can be set uniquely for each Salesforce environment. Thus, during deployment, the correct email address is used for each instance, whether it's Dev, INT, or another environment.