It looks like you don't have Dovecot installed.
Well, apparently yum doesn't do what you think it should do. When you look at the output you posted, you'll see on the bottom line
Error: Missing Dependency: MySQL-client is needed by package MySQL-bench
which means that this package is missing and the install depends on it. I'm not familiar with yum, never used it, but it seems to me that it doesn't install automatically what's needed as dependencies. So first install the mysql-client and then try again.