I use the checkpassword driver for imap/pop authentication.

To improve the performance I would like to enable authentication caching for it.

However just adding the auth_cache_size and auth_cache_ttl doesn't work. 

No entries are cached.

If I add a cache directive in the passdb, then the service doesnt start.

I was wondering if the authentication caching is supported for the checkpassword driver.

Please point me in the right direction.

Thanks in advance,

Amol