If you can hold out till v5/in 5.0beta3:
zimbraDataSourcePollingInterval
Bug 14527 - Periodic POP and IMAP aggregation and frequency and limit controls for same Quote:
Originally Posted by dbachman  I have tried installing webmin in order to schedule fetchmail to run every ten minutes or so, but it tells me there is no fetchmailrc file or users using fetchmail, even though I have created POP download accounts on most of our Zimbra accounts. |
Fetchmail requires a local user for the rights under which to run its process. That user has to have a .fetchmailrc file in their home directory, which is where the configuration settings get saved. This user doesn't have to have anything at all to do with your Zimbra mail address to which the fetched mail will be sent.
Using the user "zimbra" will appear to work when you're setting up the fetchmail process, but apparently the rights are such that you can't write the mail to that directory. Using any other local Linux user does the trick.
Pheonix uses webmin/fetchmail-he may be able to help you troubleshoot.