We have a metric which measures just that – the number of sent emails which received a reply, and the number of received emails you replied to:
You can use Advanced Filters to whittle down the information for only certain recipients or domains, and see their response rate to you. This will be shown in the "Emails Replied" chart of the report generated after the filter is applied.
For example the following filter would show me the response rate of email@example.com:
You can read all about Advanced Filters here in our Help Centre.
Please let me know if you have any more questions!