That is not possible out of the box as Q2A cannot access your email accounts. You would need to write some custom code that handles incoming emails, detect which post it relates to, then insert the reply into Q2A.
Check the docs, there are a few examples here.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.
Jan 12, 2019: Q2A 1.8.3 released!