It looks like atrpms, from whence you pulled your Dovecot 2.1 package, has Dovecot 2.2 out. But, I don't want to just upgrade if it's not something you've tested and qualified on RHEL6. And, since your repos still have 2.1, I'm guessing not.
So, is there a timeline for you to switch from Dovecot 2.1 to Dovecot 2.2 on RHEL6?
Thanks.