I was looking to delete RSS entrys by date and Relaized that the filtering in Zimbra was not as strong as it could be. Idealy we could right click on a subfiler in mail and access the filters for the sub folder that way. The Filtering should include the option "if (message) > (date) then move to (folder)"
In this case trash would be an option. I realise this is just one of the filters that should be implimented.

Additional Coment is most welcome.