Your question is too broad to answer in our Q&A format!
The steps that are needed are roughly:
Configure the server to support Active Directory authentication / integration. That is already a topic in itself with several options on how to achieve that: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/...
The original answer from 2011 is outdated.
Dovecot lifecycle announcement:
For any version before 2.2, we are not going to be providing any patches
or fixes. This has been the case before, but we are now officially
declaring them EOL.
I will still list all versions for reference. Sometimes admins have to run software they'd rather not run.